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ENAMELS 



Robert D. Landru 



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FOREWORD 

This little book is a collection of the various 
articles on Enamel published by the writer in the 
various technical journals to which credit is given 
with each article. 

There are also included some tables of interest 
to the Enameling industry and space is provided 
at the end of the volume for additional data of 
this kind. 

The book is published for the benefit of the 
Enameling industry by THE HARSHAW FULLER 
& GOODWIN COMPANY, Cleveland, Ohio, and is 
presented with its compliments. 

Robert D. Landrum 

January 1st, 1918. 



CONTENTS 

Page 
I. Enamels for Sheet Steel . . 7 

II. The Function of the Various Raw Materials in a 

Sheet Steel Enamel 15 

III. Resistance of Sheet Steel Enamels to Solution 

by Acetic Acids of Various Strengths 26 

IV. A Comparison of Ten White Enamels for Sheet 

Steel 34 

V. The Necessity of Cobalt in Ground Coat Enamels 

for Sheet Steel , 60 

VI. Methods of Analysis for Enamel and Enamel Raw 

Materials 70 

VII. Atomic and Molecular Weights and Factors used 

in Ceramic Calculations 101 

VIII. Cubical Coefficient of Expansion! 106 



ENAMELS FOR SHEET STEEL *i 

Enamels for sheet steel are boro-silicates of sodium, 
potassium, calcium and aluminum and are, in every sense 
of the word, glasses. Such enamels are so compounded 
that they form a homogeneous, glossy coating on the sur- 
face of the sheet steel utensil, which will not be corroded 
by the acids or alkalies used in cooking and which will 
resist punishment both by impact and by rapid changes 
of temperature. 

Although an enamel is a glass, the fact that it must 
adhere to steel and resist the abuse common to cooking 
utensils makes necessary the addition of other ingredi- 
ents besides those used in manufacturing ordinary glass. 
In enamels, ground quartz, flint or sand supply the silica, 
and feldspar and clay, the alumina. Fluorspar or cal- 
cite is added to supply the lime and cryolite to render 
the enamel translucent. Soda ash and pearl ash are 
fluxes adding sodium oxide or potassium oxide to the 
product, and borax furnishes the boric anhydride, which 
adds many desirable qualities, such as greater ductility 
and elasticity. Sodium or potassium nitrate is used in 
white enamels and manganese dioxide in dark colored 
enamels as an oxidizing agent. Oxide of cobalt is used 
in enamels which come directly in contact with the steel 
and adds adhesiveness to this coating. 

For producing white enamels, oxide of tin is used; 
for blue, cobalt; for violet and brown, manganese; for 
gray, nickel ; for green, copper or chromium ; for yellow, 
uranium or titanium ; and for red, iron, selenium or gold. 



♦Reprinted from the Journal of Industrial and Engineering Chemistry, Vol. 4. 
No. 8, August, 1912. 

^ Delivered before the Chemists' Club of Rochester at the University of Rochester, 
Rochester, New York, April 1, 1912. 



Enameling is still held as a secret art, and the for- 
mulas are carefully guarded. Most companies allow 
very few visitors to go through their plants and some 
keep their employees in ignorance by various schemes. 
In one American works, each of the enamel raw-materials 
is given a number. They are ordered, shipped, kept ac- 
count of, and stored under their respective numbers, and 
only those in authority even know what materials are 
used. In this same factory, employees of one department 
are not allowed in another and after being employed in 
one department, a man is barred from employment in any 
other. Some works have the formula for each enamel 
divided into two parts, one of which is mixed by one man, 
the other by a second, and certain proportions of each are 
then mixed together by a third man. In practically all 
enameling works, the materials are weighed on a scale, 
the beam of which is hidden from the laborers, who are 
also generally of foreign birth and are changed fria- 
quently. 

The "Black Shape." — The sheet steel which is used 
for enameled ware is as nearly as is possible free from 
carbon, silicon, sulphur and phosphorus, and its manga- 
nese content is generally about 0.2 per cent. These sheets 
come in squares and oblongs from 27 to 20 gauge and are 
circled, stamped and spun with as little heat treatment 
as possible and with the use of a lubricant that can easily 
be cleaned off. The ears, handles and other trimmings 
are, as far as is practical, welded on, as riveted joints are 
difficult to enamel. 

Pickling Process. — The surfaces of the completed 
steel vessels are thoroughly freed from carbonaceous 
matter by annealing at a low red-heat and are then 
pickled in hot dilute acid, thoroughly rinsed in water, 
and then in weak alkali solution. After a quick drying 
they are ready to be enameled. 

The Enamel. — In the making of an enamel, the vari- 
ous raw-materials are loaded from their respective bins 

8 



into small cars called "dollies." These are filled to a 
line which approximates the correct weight, then they 
are pulled on a scale, the beam of which is hidden from 
the workman, and the enamel-master indicates whether 
the load is light or heavy, and the workmen correct this 
by shoveling on more or taking some off. When each of 
the "dollies" is corrected so that the required amount of 
material for a mix is in it, all are dumped on a large, hard 
maple floor, the coarser material on the bottom and the 
finer on the top. This pile is thoroughly mixed by shovel- 
ing, and is loaded into an electric elevator, which hoists 
it to its bin. There is a bin for each different kind of 
enamel, and a traveling bucket which holds a melt (about 
1200 pounds) carries the mix to the tank furnaces where 
it is melted into a liquid glass. 

These tank furnaces are regenerative, reverberatory 
furnaces like those used in the manufacture of glass, and 
natural gas or crude oil is an ideal fuel for them. How- 
ever, in the older enameling works, coal is used directly, 
and in the later ones producer-gas is used as a fuel. The 
temperature required for smelting the different enamels 
varies from 1000° C. for a glaze to 1300° C. for a ground 
coat, and, in most enameling works, pyrometers are in- 
stalled to assist in controlling these temperatures. Each 
furnace will give seven or eight melts in twenty-four 
hours. 

After the enamel is melted into a liquid glass, a fire- 
clay plug in the front of the furnace is pulled out and 
the glowing liquid stream plunges out and is caught in 
a tank of cold running water. The reaction is terrific 
and the glass mass is torn and shredded, cracking into 
small pieces like popcorn, each of which is a myriad of 
microscopic seams and fissures. This "quenching," as 
the process is called, toughens the enamel and facilitates 
the process of grinding which comes next. 

The water is drained from the tanks, leaving the 
"enamel frit." This is shoveled into pans (a certain 
weight to a pan) and is ready for grinding. 

9 



In the mill room, the enamel frit is ground in large 
ball mills for about thirty hours. These mills are cylin- 
drical, about five feet long and six feet in diameter, and 
are lined with porcelain bricks. The frit is put into them 
with fifty per cent, of water and several per cent, of white 
ball-clay. For the white cover-coat enamels, tin oxide 
is also added. The mill revolves and the constant impact 
of the flint stones against the glass particles grinds them 
to an impalpable powder, which mixes with the water 
and the clay, forming a mass which has the consistency 
of rich cream. This is loaded into tanks, where it is 
allowed to age a week or so. 

Application of the Enamel. — From the mill room the 
enamel is taken to the dipping room, where it is put into 
tanks that are like large dish-pans. These are sunk into 
tables, and at each tank a slusher works. The slusher 
takes the stamped-out steel vessel, which has been 
thoroughly cleaned, and plunges it into the enamel. 
When taken out, the wet enamel forms a thin film over 
the entire surface. By a gentle swinging motion, the 
excess of enamel is thrown off, and the vessel is placed 
bottom down on three metal points projecting from a 
board. Three or four vessels are put on a board; these 
are placed on racks and when the vessels are thoroughly 
dry they are carried to the furnace room. 

The furnace room contains a long bank of muffle- 
furnaces and in these the ware is put after drying. The 
temperature in these furnaces is about 1000° C. and here 
the little powdered particles of enamel are fused together 
in a solid glass coating over the vessel, the process re- 
quiring from three to five minutes. 

Each coat is burned separately. For instance, we 
have a pudding pan that is to be a three-coat white in- 
side, turquoise-blue mottle outside. It is first dipped in 
the ground coat enamel, the excess is shaken off and the 
vessel put on a three-pointed rack and dried. After dry- 
ing, the enamel stands in little grains all over the surface 

10 



of the ware, adhering to the metal on account of the raw 
clay ground with it. At this stage every care must be 
taken, for a scraping, even of the finger nail, would take 
off some of the powdered particles of the enamel. This 
pan is then put into the muffle of the furnace, and the 
heat fuses all the little particles together, leaving a tight- 
holding vitreous coating all over the surface of the vessel. 
This fundamental coating is nearly black, due to the 
oxides of cobalt and nickel which it contains, and shines 
with a glass-like luster. 

After the vessel has cooled at the ordinary tempera- 
ture of the room, it is again brought to the slushing room, 
and here is covered with an enamel — this time a white. 
It goes through the same process as before, except that 
a black bead is brushed around the rim. On account of 
the dark color of the first coat showing through, this 
second coat, after it is burned, has a gray appearance, 
and is called the "gray coat" or "first white." The vessel 
Is again sent to the slushing room, and is dipped into a 
white enamel, the excess shaken off, and before drying 
the blue-green enamel is sprayed on the outside. 

This spraying process v/as at one time done by dip- 
ping a wire brush into the wet blue-green enamel and 
the slusher shaking it over the surface of the vessel, caus- 
ing the blue enamel to fall in little speckles all over the 
white enamel. In most factories, however, spraying ma- 
chines, which work on the principle of an atomizer, have 
been installed. A tank full of the colored enamel stands 
over the table and the enamel is forced out through a 
nozzle in a spray by compressed air. The flowing of the 
enamel is controlled by the foot of the slusher as he holds 
the vessel in the spray. The vessel is then dried and the 
coating is fused in the muffle-furnace, the result being 
turquoise-blue spots on a white background. 

The finished ware is assorted into three lots: firsts, 
seconds, and job lots. Some of the seconds and job lots 

11 



are fit for redipping. They may have some little spots 
where the original vessel was not properly cleaned and 
where, on account of the rust or dirt, the enamel did not 
adhere. These spots are filed or are held under a sand- 
blast until the exposed surface is perfectly clean, and 
then the vessel is covered with another coat of enamel. 

There are schemes for saving money in all manu- 
facturing plants, and in the enameling business a large 
part of the profit comes from the residues. For instance, 
every bit of enamel is scraped from the tanks and tables, 
all sweepings from floors are saved, and all the waste 
water from the various departments is first carried into 
catch basins, and every few days these are cleaned and 
the residue, which has settled to the bottom, is taken out. 
The residues from all these sources are again melted with 
the proper amount of fluxing material and coloring mat- 
ter, and this dark-colored enamel is used for coating the 
cheaper wares. 

A German White Enamel. — In order to give an idea 
of the composition of a white cover-coat frit, such as is 
used on cooking utensils, and to show the method used 
by ceramists to calculate its so-called molecular formula, 
the following enamel, the formula of which is taken from 
the 1911' edition of the "Taschenbuch fur Keramiker," 
is used: 

Feldspar 38.6 per cent., quartz 19.0 per cent., borax 
15.4 per cent., cryolite 11.7 per cent., saltpeter 6.5 per 
cent., calcite 6.5 per cent., fluorspar 1.3 per cent, and 
magnesium carbonate 1.0 per cent. 

Enamel Materials. — All the materials used were 
practically pure except the feldspar, which was a peg- 
matite of the following composition : 



^ Page 18. Published by Keramische Rundschau, Berlin, N. W., 21. 

12 



Per cent. 

Silica (SiO==) 70.66 

Alumina AbOs 16.85 

Potassium oxide K2O 5.93 

Sodium oxide Na^iO 4.61 

Lime CaO 0.52 

Carbon dioxide CO2 0.41 

. Moisture H2O 1.02 



This figures to a "molecular" formula of 

0.45Na^O1 r7.11Si02 

0.39 K2O y AUOs < 0.34 H2O 
0.06 CaO J 1 0.06 COs 

the molecular weight of which would be 602. 



The other materials used were : 

Equivalent 
Material Formula weight 

Quartz SiO^ 60 

Borax Na^O 2B2O3 IOH2O 382 

Cryolite 2Na3AlF6, giving 3Na20Al20s-6F2 . . . 420 

Saltpeter 2K2O N2O5 202 

Calcite CaO CO2 100 

Fluorspar CaFs, giving CaOFa 78 

Magnesium carbonate MgO CO2 84 

Feldspar (Given above) 602 

The above total corresponds to the following molecu- 
lar formula of enamel : 



0.497 Na20 1 '^^^^^: r2.513 SiO^ 
0.186 K2O L I 0.262 B^Ot 

0.278 CaO f 0.299 AI2O3 i 0.599 F2 
0.039 MgO J L 



Research Laboratory 

LiSK Manufacturing Co., Ltd., 

Canandaigua, N. Y. 

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THE FUNCTION OF THE VARIOUS RAW MATERIALS 
IN A SHEET STEEL ENAMEL* 

An enamel, such as is used on cooking utensils, is a 
glass of such nature that it will adhere to steel and on 
account of this, its composition is more complicated than 
that of ordinary glass. The materials used to make ordi- 
nary glass are sand, limestone and soda ash, with lead 
oxide added to certain types. These glasses, however, 
will not adhere to iron and have a co-efRcient of expan- 
sion entirely different from that of sheet steel, and also 
the temperature at which they must be melted would 
soften the steel shape. An enamel, then, although a glass 
in every sense of the word, and containing the elements 
introduced by these glass materials, also contains others 
added to modify the physical properties and to suit it for 
the purpose intended. 

Quartz and Flint 

Sand is the material which furnishes silica (SiOg) to 
glass and it is sometimes used in enamels. However, 
enamels must melt at a much lower temperature than 
glass and thus require the silica-furnishing material to 
be very finely powdered in order that it may combine 
with the other materials at this lower temperature. As 
it is more expensive to pulverize sand than it is to pul- 
verize quartz or flint, one of these minerals — each hav- 
ing the same chemical composition as sand — is generally 
used. 

It may be taken as a general rule that other things 
remaining constant, the higher the per cent of silica the 
higher will be the melting point of the enamel and the 



•Reprinted from original communications. Eighth International Congress of 
Applied Chemistry. Vol. XXV— Page 317. 

15 



greater its acid resistance. Silica also has a low co-effi- 
cient of expansion and increasing it in an enamel lowers 
the co-efficient of expansion of that enamel. Therefore, 
one method of regulating an enamel coating is to increase 
the silica when the enamel is inclined to split off when 
cooling after muffle burning. This remedy is indicated 
when the curve of the enamel chips, showing that the 
enamel contracts less rapidly on cooling than the iron. 

Soda Ash 

In glass, all of the sodium oxide is introduced as soda 
ash, while in enamel, this material is only used when it is 
desirable to add the sodium oxide without the introduc- 
tion of any other ingredient. 

Up to a certain point the addition of silica to 
an enamel formula may lower the melting point. An 
exaggerated example is that Calcium Oxide (lime) alone 
is practically infusible, but on adding silica, a fairly easily 
fusible glass is formed. 

Soda Ash is commercially pure anhydrous sodium 
carbonate (NaXOg) and, therefore, besides adding the 
sodium oxide to the finished enamel, gives off carbon-di- 
oxide gas during smelting and the melted mass is then 
quite thoroughly stirred by the evolution of this gas and 
many impurities are carried off. 

The function of the sodium oxide is to combine with 
the other materials (especially the silica) and form a 
vitreous product. The larger the proportion of sodium 
oxide (in comparison with the amount of silica present) 
the lower will be the melting point of the product and the 
less resistant to acids it will be. At the same time, how- 
ever, an increase of the sodium oxide tends to make the 
product more flexible and less brittle. 

Many enamels do not include soda ash in their batch 
mix formulas as sufficient sodium oxide is furnished by 
the feldspar, cryolite and borax. 

16 



Fluorspar and Calcite 

Fluorspar and Calcite are the minerals which are 
used to supply the lime (CaO) to enamels. In glass, 
limestone furnishes this important ingredient, but on ac- 
count of the impurities, always present in this mineral, 
it cannot be used in the more carefully compounded enam- 
els. Both Fluorspar and Calcite have their advantages 
and disadvantages and, as their cost is about the same, 
a careful consideration of these is necessary before one 
can decide which is the better to use in an enamel. Ameri- 
can practice is inclined to favor the use of Fluorspar. 

Fluorspar 

The calcium present in Fluorspar seems to combine 
more easily with the other ingredients of the enamel 
batch than does the calcium oxide of calcite. This is 
evident from the fact that Fluorspar enamels melt at a 
lower temperature and become homogeneous in a shorter 
time than calcite enamels. In enamels, which derive some 
of their opacity from cryolite, this is of particular advan- 
tage, for it is a well known fact that the longer a cryolite 
enamel is smelted, the less opaque it becomes. 

The disadvantages pertinent to the use of fluorspar 
instead of calcite in an enamel formula are due to two 
things ; this mineral contains fluorine and is a powerful 
reducing agent at the temperature attained in the smelter. 
The fluorine is set free during the smelting and, although 
the virtues of fluorspar are very likely due to the ener- 
getic action of this element, it is also active in corroding 
the furnace linings and the life of the smelter is short- 
ened. 

The reducing action of this mineral makes it very 
necessary to carefully regulate the smelter so that the 
atmosphere is always oxidizing and where a large amount 
is used the percentage of nitrate in the batch mix must 
be increased. 

17 



Calcite 

Calcite in enamels does not act as a reducing agent 
nor does the gas given off by it (CO2) attack the furnace 
linings. Therefore, the life of the smelter is longer and 
there is no necessity for adding more nitrate nor of so 
carefully controlling the atmosphere of the smelter. 

The disadvantages common to a calcite enamel are 
due to its requiring a higher temperature and a longer 
time to combine with the other ingredients of the batch. 
With cryolite enamels, this longer smelting is certain to 
cause them to lose some of their opacity. 

Defects Caused by Fluorspar and Calcite 

Unless sufficiently smelted and thoroughly oxidized, 
fluorspar enamels are not stable and, on standing, lose 
their gloss, while calcite enamels, unless smelted entirely 
homogeneous and free from carbonate, are inclined to 
chip and scale and to form bubbles and blowholes where 
the enamel is applied thickest. 

Calcium Oxide (CaO) 

The calcium oxide introduced by either of these ma- 
terials will replace sodium oxide in an enamel formula 
and, while not affecting the melting point to any great 
extent, makes the enamel much harder, more acid resist- 
ant, more glossy and more opaque. Calcium oxide in- 
creases the brittleness of an enamel, however, but at the 
same time it allows the addition of more boric anhydrid 
and this ingredient counteracts this effect. 

Feldspar 

Feldspar is generally included in the batch mix of 
any enamel. The new element introduced by this ma- 
terial is aluminum in the form of alumina (ALOg). It 
also adds sodium oxide (NaoO) or potassium oxide (KgO) 
or both and at a much cheaper price per pound than 
they can be bought in any other form, 

18 



The other ingredient introduced by feldspar is silica 
(SiOa) and it is likely that its introduction thus has the 
advantage over its introduction as quartz or flint, in that, 
in feldspar, nature has already combined the alumina and 
the silica. An enamel, therefore, getting its silica from 
feldspar requires less heat in smelting than one getting 
the silica otherwise. 

The alumina added by the feldspar makes the glass 
softer and also less resistant to acids, but when other 
suitable ingredients are present, causes the enamel to be- 
come translucent. It also lessens the tendency of the 
enamel to chip but makes it more liable to craze. It com- 
bines directly with the other ingredients forming a homo- 
geneous product and, therefore, does not aid in improving 
the stretching qualities of the product as does the alumina 
added as clay, which material will be taken up later. 

Borax and Boric Acid 

One of the most characteristic ingredients of an en- 
amel is boric anhydrid (BgOg) and this is furnished to 
the batch mix by borax or boric acid. 

Borax is generally used for this purpose, as it is 
much cheaper and the only enamel in which its use is 
prohibited are those whose full quota of sodium oxide is 
furnished by the feldspar and cryolite. Borax contains 
16% of sodium oxide, so in such enamels, boric acid 
(B,03.3HoO) would be used. 

Boric anhydrid (BoOg) makes the enamel more elas- 
tic, less brittle and changes the co-efficient of expansion in 
such a way that the glass produced may be used on steel. 
It is like the silica in many ways, increasing the acid re- 
sistance and allowing more alkalies and metal and earth 
oxides to be used in the mix and like silica causes the 
enamel to chip when present in excess. 

Unlike silica, however, it increases the viscosity of the 
smelted enamel and lengthens the period between the 
temperature at v/hich the enamel will melt to form a 

19 



homogeneous vitreous coating and the temperature at 
which it will "burn off," thus making the enamel less 
liable to be spoiled by poor shop practice. 

This property of viscosity, which the boric anhydrid 
increases, causes the enamel to remain thick and gummy 
on the black shape, while being heated in the muffle, in- 
stead of getting thin and running off as would ordinary 

glass. 

Clay 

Clay is always used in the mill mix of an enamel that 
is to be slushed on wet and is sometimes included in the 
ingredients that go into the smelter. In the latter case, 
it is used to introduce alumina and silica, as does feldspar, 
but without introducing any alkalies. Clay is quite in- 
fusible and very finely divided, thus adding opacity to the 
enamel. When added at the mill, it gives besides the 
qualities already mentioned plasticity to the wet enamel 
and holds up the glass particles during slushing. It also 
causes the powdered glass particles to adhere to the steel 
shape during the drying before muffle burning. 

Whether added at the mill or in the smelter, clay 
adds to the stretching qualities of the finished enamel 
coating. This is accounted for by the infusibility of the 
clay, with property keeps it from entering into complete 
combination with the other materials. Instead, it holds 
the glass masses (with which each particle of clay is sur- 
rounded) apart during the contraction of the steel and 
allows them to pull away from it without chipping dur- 
ing expansion. Under the microscope, enamels with a 
high clay content are very porous — the higher the clay 
the more porous — and, therefore, clay in an enamel al- 
ways lessens the gloss. This is the prime factor in limit- 
ing the amount of clay that can be used in an enamel. 

Stellmittle 

The plasticity of clays in water can be greatly in- 
creased by adding to the water very small quantities of 
acids, bases or salts which dissociate in the water. These 

20 



cause the clay to assume a colloidal form quite jelly-like 
in nature and thus make the enamel batch in which they 
are present much thicker without removing any of the 
water. 

These are called "Stellmittle" or fixation materials 
by the German enamelers. Any acid will answer, but, 
as the effect on the finished product is deleterious, these 
are seldom used. Borax (a saturated solution in hot 
water) or a mixture of this with a saturated solution of 
sodium carbonate is generally used in ground coat enam- 
els and may be used in small quantities in white enamels. 
Magnesium Sulfate has much favor with most enamelers 
and its principal virtue is that less of it is required than 
of any of the others. Magnesium sulfate cannot be used 
in the ground coat, as it will cause the iron to rust. 

Magnesium Oxide and Carbonate are used in the 
mill mix and are good for this purpose, as also is ammo- 
nium chloride, ammonium carbonate and ammonium ace- 
tate. Some enamelers also use the sulfate of sodium but 
any of the sulfates will impair the gloss of the product. 

Oxide of Tin 

Tin oxide is one of the most important and, at the 
same time, most expensive of the enameling materials. 
Indeed a French writer defines an enamel as "an opaque 
glaze containing tin oxide." 

Added to the smelting batch, up to about 3% of the 
stannic oxide — the commercial oxide of tin — is reduced 
to stanous oxide, which forms a transparent compound 
with the silica. All over 3%, and practically all added 
at the mill, remains in suspension in the enamel, and, 
keeping its intense white color, makes the enamel opaque. 

The writer has used as high as 30% of this material 
in an excellent, though costly, enamel, but the amount 
used in white enamels for cooking utensils seldom runs 
below 5% or above 15% in the finished product. 

21 



All efforts to entirely replace this material with a 
cheaper one have led to the conclusion that some oxide 
of tin is absolutely necessary in a white enamel. Other 
materials can replace part of it, but the question as to 
whether there is any actual saving in so doing is a matter 
of dispute. 

The higher the percentage of tin oxide in an enamel 
the thinner it may be applied and attain a given standard 
of whiteness. This thin application reduces the produc- 
tion cost in two ways, viz., less enamel is required and the 
.number of seconds, caused by the scaling off of the too 
thick coatings, will be greatly reduced. But of still more 
importance is the fact that the thin application of the 
enamel adds greatly to the durability of the ware under 
punishment both by impact and by sudden changes of 
temperature, thus adding to the reputation of the manu- 
facturer. Then too, the opacity produced by this mate- 
rial is practically "fool proof." The tin oxide substitutes 
must be handled with the greatest of care during every 
operation and the slightest variation of method of proce- 
dure is likely to spoil the enamel. 

Cryolite 

The only material which produces opacity besides 
the tin oxide and which has stood the test of time is cryo- 
lite. This material must be added in the smelter and al- 
though it adds no new elements those added are so geo- 
logically combined that at a certain temperature they 
make the enamel frit quite translucent and even opaque 
when thickly applied. The amount of this material which 
can be used in a given enamel is limited by the large 
amount of sodium oxide which it introduces. Cryolite 
is a double fluoride of aluminum and sodium and in the 
enamel about 20% of its mass escapes as fluorine gas and 
is replaced by oxygen. Thus it is very necessary to keep 
the atmosphere of the smelter oxidizing, and this is best 
done by having sufficient nitrate present in the enamel 
batch. The opacity produced by cryolite is quite elusive 

22 



and the greatest care must be taken to have the tempera- 
ture, both of the smelter and the muffle furnace, right 
and the length of time for smelting and burning correct. 

Oxide of Antimony 

Antimony Oxide is another substitute for tin oxide 
and like cryolite this is added in the smelter. Antimony- 
containing enamels are quite opaque, if applied in thick 
layers; thin coats of such enamels, however, are quite 
transparent and it is doubtful whether or not antimony 
has any great coloring effect on a properly applied 
enamel. Antimony oxide is in itself quite poisonous and 
when used in quantities large enough to give the desired 
opacity, there is a danger that some of it may be made 
soluble in the cooking acids and thus be detrimental to 
the health of the consumer. In practice most antimony 
enamels contain less than 5% of this material. 

Both antimony and tin oxide and, in fact, all metallic 
oxides add lustre to the enamel coating, for they increase 
the density and it has been shown that the gloss of a glass 
or enamel increases directly with the density. 

Zinc Oxide 

The oxide of zinc is the only metallic oxide, except 
that of tin, which can be safely added to a white enamel 
for the purpose of increasing its luster, and even it will 
lower the resistance to corrosion by acids of such an en- 
amel very markedly. 

Used in large quantities and in very soft enamels it 
produces some opacity. Its main use, however, is as a 
substitute for the objectionable lead oxide in formulas 
for colored enamels. Like lead, it has the property of 
making such colors more brilliant. 

Saltpeter and Chili Saltpeter 

Potassium nitrate (saltpeter) or sodium nitrate 
(Chili Saltpeter) is used in enamels, which require ox- 
idizing agents in the smelter. 

23 



Oxidizing agents are necessary in enamel formulas 
which contain fluorspar or cryolite to replace the fluorine 
given off in the smelter and also in white enamels con- 
taining iron as an impurity. In the latter case, they 
change all of the iron to the higher oxide which has a less 
intense coloring action on the enamel. 

Sodium nitrate is much cheaper than potassium ni- 
trate but must be stored in air tight containers as it is 
very deliquescent. The impracticability of storing the 
material has forced manufacturers to use the more ex- 
pensive nitrate or to employ a chemist to make daily de- 
terminations of its moisture content. Then too, experi- 
ment has shown that the presence of potash in an enamel 
already containing soda tends to increase the gloss and 
to lower the melting point without affecting the other 
properties. This would be a reason for using nitrate of 
potash instead of nitrate of soda in an enamel, in which 
potash is not supplied by some other material, for potas- 
sium oxide remains from the saltpeter, while sodium oxide 
remains from the Chili saltpeter. 

Manganese Di-Oxide 

Manganese di-oxide (MnOa) is a strong oxidizing 
agent and its use in enamels is primarily due to this fact. 
Used in an enamel batch, it disintegrates during smelting 
into manganous oxide (MnO) and oxygen gas and the 
latter, besides stirring the molten enamel, changes some 
of the ingredients to their highest possible oxides. 

This action is especially desirable in ground coats 
which must stand a hot fire in the muffle, as it renders 
over-burning during this operation less probable. 

Manganese compounds cannot be used in white en- 
amels in more than minute quantities as it colors the glaze 
an amethyst purple. Its second use in enamels is due 
to this coloring action and it is used in many colored 
enamels. 

24 



Oxide of Cobalt 

Oxide of Cobalt (CO3O4) is added to enamels either 
to give them a blue color or to make them adhere directly 
to the steel. For the second reason, all successful ground 
coats contain oxide of cobalt. An enamel may be so com- 
pounded that its co-efficient of expansion will be exactly 
that of the sheet steel upon which it is to be used, and, 
yet without the addition of oxide of cobalt, according 
to the writer's experience, it cannot be made to adhere 
to the steel as well as with this addition. There are 
many theories as to the exact function of cobalt in a 
ground coat enamel and the popular one at present, is that 
silicate of cobalt in the enamel frit is reduced during 
muffle burning to a lower silicate and perhaps to metallic 
cobalt. The oxygen, which is given off in either case then 
unites with the iron of the black shape and is taken into 
the enamel as ferrous silicate and, if metallic cobalt is 
left, this unites with the iron of the black shape, forming 
a widely distributed porous alloy. At any rate, there is 
an interaction between the cobalt of the enamel and the 
iron of the black shape which binds the enamel to the 
steel. Whether this is the correct explanation of the ac- 
tion, we do not know, but it is certain from practical ex- 
perience that the cobalt-containing ground coat enamels 
are more easily burned correctly by the men in charge 
of the muffle furnaces. This is explained by the fact that 
there is a definite, though delicate, color change from 
blue to green in cobalt-containing ground coat enamel? 
at just the point at which the enamel so fired will adhere 
most firmly to the steel coat. Such an enamel, when cor- 
rectly burned, will have a very characteristic greenish 
tinge; when under-burned a blue color, and, when over- 
burned, a brownish black color. 



26 



RESISTANCE OF SHEET STEEL ENAMELS TO 
SOLUTION BY ACETIC ACIDS OF 
VARIOUS STRENGTHS* 

Certain enameled wares have been advertised as 
capable of withstanding 80 per cent, or 90 per cent, acetic 
acid solutions, and although this was found to be a true 
statement still it was misleading, for these very wares 
were unable to resist the action of ordinary vinegar which 
contained but 5 per cent, acetic acid. This phenomenon 
is explained by the chemist as being due to the fact that 
a 5 per cent, solution of acetic acid is very much more dis- 
sociated than one of 80 or 90 per cent, and therefore its 
dissolving action (which is directly proportional to its dis- 
sociation) is much the greater. 

To show the action of various mixtures of this com- 
mon cooking acid and water, the two series of tests were 
made upon enamels typical of some of the cheap wares 
on the market. 

The First Series of experiments was made upon a 
gray enamel, mottled with dark brown. As the dark 
enamel was made up from residues, and as the propor- 
tions of the two enamels on the dishes is uncertain, the 
exact molecular formula of the finished enamel coating 
cannot be given, but the formulas as calculated from the 
batch mix of the gray enamel and the analysis of the dark 
enamel frit (before milling) is given below. 



0.667 NaaO 
0.108 K2O 
0.083 CaO 
0.057 MgO 
0.085 ZnO 



THE ENAMELS 
Soft Gray EnameP 

1.065 Si02 



y 0.272 AbOs 



0.402 B2O3 



.0.532 F2 
Milled with 7% clay 



*Reprinted from Transactions of American Ceramic Society. Vol. XIII, page 494. 

1 So called, as it is translucent instead of opaque and when milled without tin 
oxide — as was the case above — the dark ground coat shows through giving a gray 
effect. 

26 



Soft Dark Enamel for Spray 



0.430 NasO 
0.083 K2O 
0.200 CaO 
0.045 MgO 
0.056 CuO 
0.010 CoO 
0.176 MnO 



0.114 AI2O3 



rl.700 SiOi 



0.430 BaO* 



0.178 F^ 
Milled with 7% clay 



The Test 

Nineteen miniature wash-basins about 8.5 centi- 
meters in diameter and 2 centimeters in depth were 
slushed and burned in a dark colored ground coat, and 
then dipped into the gray enamel slush and when the 
excess was shaken off a light spray of the dark-colored en- 
amel was flipped in with a brush. After drying they were 
burned at about Seger cone 09 in a muffle furnace. They' 
were cooled in a desiccator and weighed accurately to 
one-tenth of a milligram (0.0001 gram). Into one of them 
was accurately measured (from two burettes graduated 
to 1/10 of a cubic centimeter) 0.25 cubic centimeter acetic 
acid^ and 24.75 cubic centimeters distilled water, making 
a 1 per cent, solution by volume. Into a second dish was 
measured (as before) sufficient acid and water to make 
a 2 per cent, solution. Into a third a 3 per cent, and so on 
as given in the table following. These basins were then 
placed upon a gas hot-plate and evaporated to dryness 
without allowing them to boil vigorously. 

When baked dry (fifteen minutes after apparent dry- 
ness) the dissolved residue was washed out at the tap, the 
dishes were scrubbed with a finger covered with a rubber 
finger-stall, rinsed thoroughly with distilled water, placed 
upon the hot-plate again until dry, cooled in a desiccator 
and again weighed. The loss in weight, which is equal 
to the amount of enamel dissolved in each case, is given 
below in milligrams. 



^ This acetic acid was the ordinary 
tained 98.99% acid by weight. 



c. p. 99% (1.05 sp. gr.) and by analysis con- 



27 



The Results 

Enamel Enamel 

Per cent dissolved Per cent dissolved 

acid Mg acid Mg 

1 4.8 25 17.9 

2 6.9 30 18.9 

3 10.1 40 13.0 

4 12.1 50 8.9 

5 14.9 60 5.0 

7 16.9 70 3.1 

9 18.5 80 1.6 

15 21.3 90 0.3 

17 22.0 100 0.0 

20 22.4 



The Second Series was undertaken upon an enamel, 
the definite molecular formula of which can not be given. 

The Enamel used was "soft gray enamel," the 
molecular formula of which is given above. 

The Test used was the same as with the first series 
except that the miniature wash-basins were slushed and 
burned in three coats, viz., a dark ground, a good opaque 
white, and the "soft gray enamel" given above which 
was the top coat. These dishes are on exhibition and 
the results are given in the following table. 





The 


Results 






Enamel 




Enamel 


Per cent 


dissolved 


Per cent 


dissolved 


acetic acid 


Mg 


acetic acid 


Mg 


1 


3.4 


21 


14.0 


2 


5.7 


23 


12.0 


3 


7.0 


25 


9.9 


4 


9.3 


30 

40 


11.3 


5 


11.5 


10.3 


7 


15.1 


50 


7.9 


9 


15.9 


60 


4.6 


11 


16.3 


70 


, 2.8 


13 


16.6 


80 


1.4 


15 


16.7 


90 


0.2 


17 


16.3 


100 


0.0 


19 


14.7 







28 



The Enamel Solubility Curves 

The accompanying sketch shows graphically the re- 
sults of these two series of experiments. The various 
percentages of acetic acid solutions are laid off horizon- 
tally and the lengths of the vertical lines are proportional 
to the amount of enamel dissolved by the corresponding 
acid, one centimeter length of vertical line being equal 
to one milligram of dissolved enamel. The results of the 
first series, i. e., the one using the mottled enamel, are 
marked "X," while those of the second series, i. e., of 
the solid-colored enamel are marked "o." 

N. B. The dip of the two curves from 21 per cent, to 
30 per cent, acid is unexplained. Several independent 
trials at those points tended towards proving that this dip 
is not due to experimental error. 

Discussion 

MR. STALEY: This paper is interesting and in- 
structive. As a practical method of testing the relative 
solubility of enamels in acid solutions, the method de- 
scribed has the commendable feature of being easily and 
rapidly performed. In point of accuracy, it is capable of 
being materially improved. 

The shape of the solubility curve derived is very in- 
teresting. That the solubility should decrease as the acid 
becomes very concentrated is in accord with common ex- 
perience.^ But why should the solubility be greatest at 
15 to 20 per cent, acid? Dissociation can hardly be at a 
maximum at this high concentration. Nor are we willing 
to grant that the solvent action of acetic acid is directly 
proportional to its dissociation. If we leave out of con- 
sideration the possibility that the acid solution may act 
toward the enamel simply as a solvent, dissolving it as 
water dissolves sugar, and treat the phenomena as a case 
of chemical attack by an acid, we must keep in mind the 
following considerations : 



^ Foerster, "Action of Acids on Glass," Zeitschrf . Instraum., XIII, 457. 

29 



X ""t 






%i 




CJ 




O 




V) 






^ 


,fe 


ki 


^ ^ 


\ 


V ^ 


Q- 


^ ^ 


;::^ 


^ .1^ 


to 




X 


1^ S ^ 


k 




^ 


^^ ^ 


■^Q 


^ n^ 


■> 


X ^ 




^ ^ ^ 


---1 


\ ^ k 


t^ 


k '^ ^ 




^n 


:i 








■^ 


f?> "^ 


^r 


Q. 


^ 




kj 





p0^/ossip /sujoug /o swsjE^i/ij^ «, 



30 



1. In dilute acid solutions, the acid is more disso- 
ciated than in concentrated solutions. This of itself means 
simply that we will have more action in a given time per 
unit of acid and does not mean that the more highly ion- 
ized acid is capable of dissolving more enamel if the reac- 
tions are allowed to come to equilibrium. 

2. Dilute acid solutions contain fewer units of acid. 

3. Very highly concentrated acid solutions have 
little action. 

4. The concentration of the acid solutions varied 
continuously as they were boiled, becoming more and 
more concentrated as the boiling progressed. Therefore, 
the more dilute the acid the longer the time in which ac- 
tive concentrations would be operating. It also follows 
from this that the slower the rate at which the acid is 
concentrated, the greater will be its solvent action. 

In accordance with these conflicting tendencies, we 
find the acid solutions of maximum solvent action are 
those of medium concentrations. 

Acetic acid is one of the few organic acids that does 
not form a mixture of constant boiling point with water. 
The pure acid boils at 118° C. and in water solutions the 
water will start to come off at 100°C., and will come off 
the more rapidly the higher the temperature. So, if we 
should start with a given volume of what would be in this 
method approximately a 5 per cent, solution by volume 
of acetic acid and place it on a hot gas plate, we would 
soon have a smaller volume of 10 per cent., then 20 per 
cent, and so on up to a very small volume of 100 per cent, 
acid. The resulting solvent action would probably vary 
materially from what would be obtained by a treatment 
for a given time with an acetic acid solution of 5 per cent, 
strength. The latter results which would truly corre- 
spond to the title of the paper under discussion could be 
obtained by the use of a return condenser. 

31 



In order to determine the effect of the rate of evapo- 
ration on the solvent action of an acid solution of given 
strength, the following tests were made by the writer. 
Four pans coated with the same enamel were treated 
according to this method, the only variation in their treat- 
ment being that two pans were placed on a hot portion 
and two on a cooler portion of the same gas hot-plate. 
Violent boiling did not occur in either case. 

The results are tabulated below: 

Time for Enamel 

Per cent of evaporation dissolved 

Nc- of sample acetic acid in minutes Mg 

1 15 65 20.9 

2 15 65 19.1 

3 15 155 37.8 

4 15 155 39.0 

It would seem that in a test of this kind a constant 
temperature bath should be employed. 

MR. LANDRUM : I agree with Mr. Staley that my 
title is rather misleading and might infer that this paper 
is intended as a research in pure chemistry instead of 
being merely a statement of the results of a series of 
practical tests made to demonstrate in a quick and con- 
vincing way the fact that an enameled ware may with- 
stand the action of boiling 90 per cent, acid and still be 
attacked by acid solutions even as dilute as those used 
in cooking. 

In these tests the conditions were very carefully kept 
as uniform as possible, and I might add that acetic acid 
and the method of boiling to dryness were used simply 
because I was trying to duplicate the method used on the 
ware advertised as "90 per cent, acid proof." I also 
would like to state that in these series of tests all the 
dishes in each series were put on the hot plate at the same 
time and that this plate was of the type given an even 
temperature to all parts of the plate (see E. H. Sargent's 
catalog for cut of plate No. 2406). While, as stated, the 

32 



solutions w.ere not allowed to boil vigorously, they were 
allowed to boil down as rapidly as possible without spat- 
tering. From eighteen to twenty minutes were required 
to boil to dryness. 

I certainly do not advocate this as a method for test- 
ing the acid-resistance of enameled wares and agree with 
Mr. Staley that for a research as that seeminly indi- 
cated by my title, a constant-temperature bath and a re- 
flux condenser should be used. However, for purposes 
of duplicating the treatment received by an enameled 
dish in actual use this method of showing the action of 
various acetic acid solutions might have some points in 
its favor over the more accurate one suggested. 



33 



A COMPARISON OF TEN WHITE ENAMELS FOR 
SHEET STEEL* 

This paper is the record of the manufacturing and 
description of the physical properties of ten white enam- 
els. It is given not with the idea of presenting to ceramic 
literature a set of commercial formulas, but to illustrate 
a method for testing, arranging the data, and arriving 
at the comparative values of any enamels upon which it 
might be desirable to experiment. 

The ten enamels are those given in the *'Taschenbuch 
fiir Keramiker, 1911,"^ pages eighteen and nineteen. It 
should be stated, however, that some changes have been 
made in the milling where it was deemed necessary, and 
also that a feldspar high in silica has been used where 
the formula calls for pure feldspar. 

All the materials, except the borax and the saltpeter, 
were finely ground. Crystals of these were used. The 
enamel batches were weighed, a kilogram at a time, on 
a balance sensitive to one hundredth of a gram. They 
were then very thoroughly mixed and were smelted, 200 
grams at a time, in a gas-fired crucible furnace,^ at tem- 
peratures varying from 1050° to 1200° C. This smelting 
required from twelve to twenty-five minutes and, as is the 
custom in practice, the molten enamel was poured into 
cold water to facilitate subsequent grinding. 

The resulting frits were milled — after drying^with 
the required amount of tin oxide, clay, magnesia and 

* Reprinted from the Transactions of the American Ceramic Society. Vol. XIV. 
(Paper read at Chicago, 111., Meeting, March, 1912.) 

> Published by the Keramische Rundschau, Berlin, N. W., 21, Germany. 

2 See E. H. Sargent's Catalogue No. 2098 for illustration and description of this 
furnace. 

84 



water, about four hundred grams at a time, in a small 
porcelain ball mill. (This mill is manufactured by the 
Abbe Engineering Co., N. Y., and is illustrated on page 
eleven of their catalogue.) The time required for mill- 
ing varied from 3^/^ to 6% hours. 

The wet enamel from the mill was slushed upon minia- 
ture wash basins which had been previously coated with 
a good cobalt groundcoat. After drying and burning, a 
second coating of the same white enamel was applied. 
Both white cover-coats were applied as thin as possible 
and were burned in the regular muffle furnaces. 

These dishes were then tested as to their resistance 
against corrosion by acetic acid; their behavior during 
rapid expansion and contraction; and their brittleness, 
elasticity and adhesiveness under punishment by impact; 
and were examined as to their opacity, gloss, etc., as a 
finished ware. 

METHODS FOR TESTING THE WARES 
Test as to Corrosion by Acetic Acid 

Each dish was carefully dried and weighed correctly 
to 0.0001 gram; and 15 cc. of 20 per cent, acetic acid^ 
(20 per cent, by volume of 99.5 per cent, acid) were 
measured into it. It was then placed on a gas-fired hot 
plate and boiled to dryness, the plate being so regulated 
that about thirty minutes were required to bring the ves- 
sel to dryness. The enameled dish was then washed out 
thoroughly with distilled water, rinsed, dried on the hot 
plate, cooled in a desiccator and again weighed. The 
difference in weight is the amount of enamel dissolved 
by the acid, and is recorded as "Acid Loss." The ten 
enamels were then arranged in a list according to their 
relative resistance to corrosion, the dish losing the least 
being first, and so on. The position of each enamel in 
this list is also given under "Acid Loss." 



' This has been shown to be about the strongest mixture of acetic acid and water, 
as measured by its action on an enamel. See page — . 

35 



Tests of Adhesion Under Rapid Expansion and 
Contraction 

Test 1. — Twenty-five cubic centimeters of water 
were heated to boiling in the dish, on a wire gauze over 
a Bunsen flame, and the dish was then plunged into cold 
water. The effect of this treatment on the enamel was 
recorded. 

Test 2. — The dish from Test 1 was dried, heated on 
the wire gauze over the Bunsen flame for one minute, and 
then plunged into cold water and any results noted. 

Test 21/2. — In the dish from Test 2 a few cubic centi- 
meters of water were boiled away — over the Bunsen flame 
as in the other two tests — and then the dish was allowed 
to remain, dry, over the flame for one minute and was 
again plunged into cold water. (This test may seem a 
duplication of the one above. It is not; many commercial 
wares fail with this test as it is especially severe.) 

Test 3. — The dried dish from Test 21/^ was very 
gradually heated in the blast flame until the bottom be- 
came red-hot. The results of this rapid expansion were 
noted. 

^ Test 4. — While the dish was still red-hot from Test 3 
it was plunged into cold water and the effect of this rapid 
contraction upon the enamel coating was recorded. 

A description of the behavior of each enamel under 
these tests is given under "Expansion and Contraction," 
and it is to be noted that when a test is not mentioned 
the ware was unaffected by it. Again the enamels have 
been listed, this time according to their adhesiveness 
under rapid changes of temperature, and their position 
in this list is also given under "Expansion and Contrac- 
tion." 

36 



Test as to Adhesion Under Punishment by Impact 

A testing machine, by means of which a five-pound 
hammer with a three-quarter inch rounded head can be 
dropped twenty and one-quarter inches onto the middle 
of the bottom of the inverted basin, was used. The sam- 
ple dishes were weighed correctly to 0.01 gram before 
and after the hammer was dropped upon them, and the 



rf?ANS- AM. CERSOC VOL.MV LAA/eWM 



fliL_^._ITT 



■c^ 



Impact Testing Machine. 

grams loss and a brief description of the effect upon the 
enamel coating is recorded under "Loss under Hammer." 
As before, the enamels have been arranged in a list which 
shows their relative adhesion under punishment by im- 
pact. 

Examination as to Opacity 

The finished dishes were arranged in a series accord- 
ing to their opacity, and their position in this series as 
well as other details as to their appearance are given 
under "Appearance of the Ware." 

37 



Arrangement of the Data 

It is the custom of the Lisk Manufacturing Com- 
pany's laboratory to make a complete record of each 
enamel on a single sheet of special form, and although 
this cannot be followed exactly in publishing this article, 
the general arrangement and form of report will be re- 
tained. 

Immediately under the heading of the enamel the 
batch mix in percentages and the calculated graphic 
formula is given, and under the latter the oxygen ratio 
and the ratio of the silica to the boric anhydride 

Material Formula Equiva- Loss Cost 

lent on per 

Feldspar* 0.45 NaaO, 0.39 K2O, weight ignition pound 

0.06 CaO, AI2O3, 7.11 SiO^. .602 1.43% $0.0035 

Borax Na^O, 2B2O3, IOH2O 382 47.0 0.0375 

Quartz Si02 60 0.0025 

Cryolite 2Na3AlF6 420 20.0 0.0600 

Soda Na^O, CO2 106 41.5 0.0085 

Fluorspar CaFa 78 28.2 0.0045 

Calcite CaO, CO2 100 43.9 0.0060 

Saltpeter K2O, N2O5 202 53.4 0.0525 

Carb. magnesia. .MgO, CO2 84 52.1 0.0800 

Magnesia MgO 40 0.1000 

Clay AI2O3, 2.8 SiO^, 1.6 H2O 300 10.0 0.0100 

Tin oxide SnOs 151 0.4600 

* Chemical analysis of feldspar : 



Per cent. 

Silica 70.66 

Alumina 16.86 

Potash (K2O) 5.93 

Soda (NaoO, by difE.) 4.61 

Lime (CaO) 0.52 

Carbon dioxide 0.41 

Water 1.02 



100.00 



(SiOa/BgOg). The oxygen ratio is given considering 
AI2O3 both as a base (ORb) and as an acid (ORa). Fol- 
lowing these ratios is the calculated loss on smelting. 

38 



^J ^) ^) ^J 










INSIDES 



^^■*^ Ji^ffil ^^•fcp-***^ 



A chemical analysis of each of the materials used 
was made, and from them the following formulas were 
derived. These and the other constants given in the table 
above were used in making the calculations. 

A brief description of the action of each enamel dur- 
ing smelting and of the resulting frit is given. The mill- 
ing follows in percentages of the weight of frit charged. 
Thus "12 per cent, tin oxide" means "12 grams of tin 
oxide to each hundred grams of frit." Water is added 
to each milling equal to 50 per cent, of the weight of 
the frit. 

The latter part of the record of each enamel needs 
no further explanation. 

The Charts. — Figs. 2 and 3 show a method of ar- 
ranging all the data in regard to an enamel in such a 
form that it may very easily be compared with any other 
enamel. The data of the enamels may be separated by 
cutting along the horizontal lines of the chart and these 
slips can be arranged in any order desired for making 
comparisons. This is especially desirable in a series 
where but one factor is changed at a time . 

The Photographs of the Dishes. — The two half-tones 
show the effect of the "Hammer Test" and the "Expan- 
sion and Contraction Tests" upon both the outside and 
inside enamel coatings of the ten wares. 

Remarks. — The types of these enamels are so differ- 
ent that the writer will not try to draw any conclusions. 
In figuring the graphic formulas the customary method 
has been used. In figuring the oxygen ratio, the tin oxide 
and the fluorine have been ignored. This is incorrect in 
almost every case, for it has been proved by experiment 
that only about 20 per cent, of the fluorine is driven off, 
and it is also a fact that some of the tin oxide combines 
to form stannous silicate. This is especially shown in 
Enamel X, for although this melted enamel contains 11.7 

43 



per cent, of tin oxide, it is a transparent glaze. Enamel 
II also illustrates this, for although its oxygen ration is 
4.5 when figured in the ordinary way, it is one of the most 
easily smelted of the enamels under discussion. 

Enamel I 

Feldspar 38.6% 0.497 NasO ^ [2 513 SiOz 

Quartz 19.0 0.186 K^O l q ngg AbOa J 262 B2O3 

Borax 15.4 0.278 CaO f ^-^^^ ^^''^^ 1 n^QQ F 

Cryolite 11.7 0.039 MgO ^ [U.&yy i^2 

Saltpeter 6.5 

Calcite 6.5 ORb = 3.1 ORa = 6.7 SiOs/B^Os = 9.6 

Fluorspar 1.3 

Mg carbonate .... 1.0 

Loss on Smelting. — 17.34 per cent. 

Milling. — Four hours with 12 per cent, tin oxide, 7 
per cent. Vallendar clay and 14 pei* cent, magnesia. 

Smelting. — Smelted at about 1200° C, hundred gram 
batches required about 15 minutes. The melted enamel 
is quite viscous and is inclined to be lumpy. 

The Frit. — The frit is fairly opaque but is translu- 
cent in spots. 

Acid Loss. — 0.0101 gram (fifth in list). 

Expansion and Contraction. — This ware was unaf- 
fected by heating to redness in blast flame (Test 3) and 
came off only over a medium sized surface on the outside 
and a comparatively small surface on the inside when 
plunged, red-hot, into cold water. This enamel is very 
adhesive, according to this test, and is second only to 
Enamel II. 

Loss Under Hammer. — This was 1.07 grams, and the 
manner in which the enamel comes off shows it to be of 
average brittleness and elasticity. It is placed fifth in 
the list according to this test, but it is to be noticed that 

44 



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46 



all the enamels, excepting VIII, which is much the best, 
and IX and III, which are much the worst, stand very 
close together. 

Appearance of the Ware. — This ware sets a very 
high standard in its appearance and is much more opaque 
than many with higher tin oxide content. In fact, it 
would be marketable with a much smaller proportion of 
this oxide added at the mill, and with this change would 
be a good commercial enamel. As it stands, it is fourth 
in the list, according to opacity. 

Cost. — The cost of the materials for the finished 
enamel is $6.70 per hundred pounds; and this could be 
reduced by using less potassium nitrate, and, as said be- 
fore, by using less tin at the mill. 

Remarks. — If the cost is not considered, but consid- 
ering everything else, this is the second best enamel of 
the ten. If cost is considered, it is the very best. 

Enamel II 

Quartz 29.7% 0.563 Na^O ) ( 1.636 Si02 

Tin oxide 24.0 0.131 K2O [ j 0.396 B2O3 

Borax 22.9 0.306 MgO )(. 0.525 SnOa 

Sodium carbonate 11.7 

Saltpeter 8.0 OR = 4.5 SiO^/BsOa = 4.1 

Magnesia 3.7 

Loss on Smelting. — 19.89 per cent. 

Milling. — Six and three-fourths hours with 4.3 per 
cent, quartz, 2.1 per cent, tin oxide and 8 per cent. Val- 
lendar clay.^ 

Smelting. — Smelted at about 1200° C, hundred 
gram batches required about 15 minutes. To get the 
maximum opacity it was necessary to mechanically stir 
just before pouring. The viscosity was medium and melt 
was free from lumps. 

The Frit. — The frit was extremely opaque and quite 
hard and tough. 

' Necessary for correct slushing but not given in original directions. 

47 



Acid Test. — The acid test showed this enamel to be 
absolutely unaffected by 20 per cent, acetic acid solutions, 
and thus it is first in the list as to resistance to corrosion 
by acid. 

Expansion and Contraction. — When plunged, red- 
hot, into cold water (Test 4) this enamel came off over 
very small surfaces, both inside and outside, and in such 
a manner that it is easily singled out as the most adher- 
ent enamel of the ten. Few enamels have ever been 
tested by the writer that have withstood sudden changes 
of temperature as well as this one. 

Loss Under Hammer. — This was 1.02 grams. This 
enamel is of average brittleness and elasticity and is 
placed third in the list as to adhesion under punishment 
by impact, but an examination of the sample used for this 
test shows that it is not as v^^ell suited to the ground coat 
as is Enamel I. 

Appearance of Ware. — This ware is very opaque, 
and it certainly should be, as the finished enamel contains 
something like 32 per cent, of tin oxide. It is second in 
opacity only to Enamel VI, which contains a little over 
23 per cent, of tin oxide when on the ware. This enamel 
is so opaque that it may be put on in very thin coatings. 
This is an advantage, as the thinner the enamel is applied 
the more durable the product. 

Cost. — The cost of this enamel is $15.07 per hundred 
pounds, and this would make it entirely impractical to 
use on a commercial ware. It is a freak enamel in every 
sense, and is of interest on this account. 

Enamel III 

Borax 30.0% 0.894 Na20 ^ f 2.217 SiOa 

Feldspar 22.0 0.097X^0 1 0.147 Al=03<^ 0.632 BsOs 

Quartz 17.5 0.009 CaO J 1 0.399 SnO^ 

Tin oxide 15.0 

Sodium carbonate .13.5 ORb = 4.4 ORa — 6.8 SiOs/B^Os = 3.5 
Saltpeter 2.0 

48 



Loss on Smelting. — 21.08 per cent. 

Smelting. — Smelted at about 1200° C. for 15 minutes 
or less; the melt pours with medium viscosity. 

The Frit. — The frit was creamy-white and very 
opaque. Some of the tin oxide remained in suspension, 
but, except for this, the frit was homogeneous. 

Milling.'' — Five hours with 10 per cent. Vallendar 
clay, and 1/4 per cent, magnesium oxide. 

Acid Loss. — The acid loss was but 0.0016 gram. This 
is remarkably low and places this enamel second in the 
list as to acid resistance. 

Expansion and Contraction. — This too is an excellent 
enamel, according to the manner in which it withstands 
punishment by rapid changes of temperature. It was 
unaffected by any of the tests up to Test 4 and when 
plunged, red-hot, into water during this test came off in 
flakes, both from the inside and outside of the dish. Very 
little steel was laid bare, but the surface of the ground 
coat enamel which was exposed is larger than on either 
Enamel I or Enamel II. This enamel is placed third on 
the list. 

Loss Under Hammer. — This was 1.31 grams. This 
shows up the chief fault in this enamel — brittleness and 
lack of elasticity — and places it next to last in the list, 
arranged in accordance with their relative ability to with- 
stand punishment by impact. 

Appearance of Ware. — Considering the fact that this 
enamel contains about 19 per cent, of tin oxide when on 
the ware, it is very poor in opacity indeed. The writer 
has made many white enamels with no other opacifier 
than cryolite that were more opaque than this one. It is 
fourth from the poorest among these ten. 



^ Original directions gave no milling. 

49 



Cost. — The cost of this enamel is $9.81 per hundred 
pounds. If the cost is not considered, this enamel stands 
fourth, considering all its properties. 

Enamel IV 

Quartz 31.40% 0.834 Na^O ] ( o kui q^o 

Feldspar 23.50 0.098 K^O L 249 ..„q\ o272 B.Os 

Cryolite 15.70 0.007 CaO ^^-^^^ AbO^y.ZlZ B2US 

Borax 16.20 0.061 MgO -> |u./zira 

Bodium carbonate. 9.30 

Saltpeter 3.10 ORb = 3.4 ORa = 6.8 SiOz/B^Oa = 9.5 

Magnesia 0.80 

Loss on Smelting. — 16.61 per cent. 

Smelting. — Smelted at about 1100° C, four hundred 

gram batches required 15 minutes. The viscosity of the 
melt was medium. 

The Frit. — The frit had little, if any, opacity and 
with a smelting of 18 minutes became a clear glass. 

Milling. — Four hours with 6.67 per cent, tin oxide, 
4.44 per cent. Vallendar clay, and i/4 per cent, magnesia. 

Acid Loss. — 0.0033 gram, placing this enamel third 
on the list. 

Expansion and Contraction. — While being heated to 
dryness (Test 2I/2) innumerable "nail chips" flew off, 
both from the inside and outside surface, and when 
heated to redness in the blast flame (Test 3) a few more 
came off. When plunged red hot into cold water (Test 
4) the coatings peeled off over medium sized surfaces, 
leaving the ground coat almost bare. Notwithstanding 
the apparent adhesiveness under Tests 3 and 4, the utter 
failure of this enamel under Test 2% causes it to be 
deemed the poorest of the ten, according to its resistance 
to punishment by rapid changes of temperature. 

Loss Under Hammer. — This was 1.07 grams; and 
although this is not far different from several others, the 

50 



manner in which the remaining enamel adhered places 
this ware sixth in the list. 

Appearance of the Ware. — Although this enamel 
contains but eight per cent, of tin oxide in its finished 
coating, it is opaque enough to be placed fifth in the list. 
The gloss is quite poor. 

Cost. — The cost of this enamel is $5.03 per hundred 
pounds. Its final rating places it fifth in the list. 

Enamel V 

Feldspar 35.30% 0.504 NasO ] r2.447 SiO^ 

Quartz 20.50 0.176 K^O U. 281 Al=0s4 0.284 B2O3 

Borax 16.80 0.320 CaO J lo.636 F2 

Cryolite 12.00 

Calcite 7.00 ORb = 3.1 ORa = 6.6 SiOVB^Oa = 8.6 

Saltpeter 6.40 

Fluorspar 2.00 

Loss on Smelting. — 17.86 per cent. 

Smelting. — Smelted at about 1100° C, in from 18 to 
20 minutes. The melt, when poured, was very thick and 
sticky. This mixture is inclined to melt unevenly and 
should be mechanically stirred for best results. 

The Frit. — The frit has a translucent white color, 
fairly good for the amount of cryolite it contains. It is 
not noticeably hard and tough. 

Milling. — Five hours with 11.76 per cent, of tin 
oxide, 5.88 per cent, of Vallendar clay, and 14 per cent, 
magnesia. 

Acid Loss. — 0.0084 gram. This is of about the same 
acid resistance as the best wares on the market and is 
excelled only by Enamels I, II and IV in this list. 

Expansion and Contraction. — When boiled to dry- 
ness on asbestos gauze, this enamel chipped slightly 
(Test 21/^) but was not further affected when plunged 

51 



into cold water. When heated to redness (Test 3) more 
chips flew off the outside and the inside enamel blistered 
somewhat. When plunged, red hot, into cold water ac- 
cording to Test 6, the enamel came off very badly from 
both surfaces of the dish, and much steel was laid bare. 
This enamel stands sixth according to this test, and is 
typical of the action of many of the wares on the market. 

Loss Under Hammer.— This was 1.00 gram, showing 
this enamel to be quite elastic. It stands next to the best, 
according to this test. 

Appearance of the Ware. — This ware is quite 
opaque, standing third among the ten, but when one con- 
siders that 12 per cent, of cryolite was used in the smelt 
and that the finished enamel contains 12 per cent, of tin 
oxide, he comes to the conclusion that much of the color 
must have been lost. 

Cost. — The cost of this enamel is $6.67 per hundred 
pounds and its final rating places it third best, when all 
its physical properties are considered. 

Enamel VI 

?roxide-::::::u;SS «i«|i'0 W^^^^^-oAltllf:''' 

Sodium carbonate. 9.00 "-^^d UaU J lo.222SnO. 

Quartz 8.00 

Fluorspar 6.00 ORb — 2.7 ORa = 5.0 Si02/B203 = 3.8 

Cryolite 5.00 

Saltpeter 3.00 

Loss on Smelting. — 20.71 per cent. 

Smelting. — Smelted at about 1150° C. in from 20 to 
22 minutes. The viscosity of this enamel was rather low. 

The Frit. — The frit was creamy-white and quite 
opaque but inclined to be non-homogeneous. Threads of 
this enamel were brittle. 

52 



Milling; — Five hours with 9.3 per cent, tin oxide, 7 
per cent. Vallendar clay, and 14 per cent, magnesia. 

Acid Loss. — 0.0190 gram, placing this enamel eighth 
on that list. 

Expansion and Contraction. — During Test 3 a few 
large chips came off while the dish was being heated to 
redness in the blast flame. When plunged red-hot into 
cold water, a large surface of the ground coat was laid 
bare on the outside, but the inside was affected very much 
less. This enamel is seventh best, according to this test. 

Loss Under Hammer. — This is 1.13 grams, which is 
the average, but places this enamel third from the last 
when listed according to its relative resistance to punish- 
ment by impact. 

Appearance of the Ware. — This is the best appear- 
ing enamel of the ten, and its great opacity is not to be 
wondered at when we consider that as a finished enamel 
it contains about 23 per cent, of tin oxide. The gloss is 
splendid. 

Cost. — The cost of this enamel is $11.10 per hundred 
pounds; but as much more oxide of tin has been used 
than is necessary for even a very high grade ware, this 
could be greatly reduced. Considering everything, this 
is the sixth best enamel of the ten. 

Enamel VII 

Feldspar 39.00% 0.500 NasO ^ r2 525 SiOs 

Q^^^^ f-00 0.179 K.0 0.303 A1.03 0:255 B.0» 

Borax 15.00 0.282 CaO f. rqo -r^ 

Cryolite 12.00 0.039 MgO J ^ 

Calcite 7.00 

Saltpeter 6.00 ORb = 3.0 ORa =z 6.7 SiOa/BsOs = 9.9 

Fluorspar 1.00 

Mg carbonate . . . 1.00 

Loss on Smelting. — 17.09 per cent. 

Smelting. — Smelted at about 1200° C. The melt 
poured thin and somewhat lumpy. 

53 



The Frit. — The frit was quite translucent and non- 
homogeneous, a hard glassy frit. 

Milling. — Three and one-half hours with 11.1 per 
cent, Vallendar clay and 14 per cent, magnesia. 

Acid Loss. — 0.0204 gram, or next to the worst in the 
ten. 

Expansion and Contraction. — This enamel chipped 
somewhat when boiled to dryness in Test 2V2> but no 
more chipping was observed while heating to redness in 
blast flame (Test 3). When plunged, red-hot, into cold 
water (Test 4) the enamel adhered fairly well, especially 
on the inside, but the failure in Test 21/2 places this 
enamel next to the poorest, according to this test. 

Loss Under Hammer. — This was 1.06 grams and this 
ware comes fourth as to its adhesiveness under punish- 
ment by impact. 

Appearance of Ware. — Considering the fact that 
there is no oxide of tin in this enamel, it is quite opaque 
indeed and deserves further trial with tin oxide added at 
the mill. Even as it stands, it Is more opaque than Enamel 
X, which contains almost 12 per cent, of tin oxide. It 
stands next to the last in the list, arranged according to 
the relative opacity of the ware. 

Cost. — On account of the absence of tin oxide in the 
make-up of this enamel, its cost is but $2.17 per hundred 
pounds. With the proper addition of this oxide at the 
mill, this enamel would cost about $5.00 per hundred 
pounds. Everything except the cost considered, this 
enamel is rated as ninth best. 

Enamel VIII 

Feldspar 38.40%^^^-,^^^ ] r 1.509 SiOs 

Borax 27 80 ^;55i ^JT 0.203 AbOa ^'^^^ B.Oa 

Tm oxide 13.90 n 99s r^n ] 0.215 F2 

Sodium carbonate 11.30 "-^^^ '-a^ J 10.293 SnO^ 

Fluorspar 5.30 

Saltpeter 2.00 ORb = 2.7 ORa = 5.0 Si02/B203 = 3.3 

Quartz 1.30 

54 



Loss on Smelting. — 20.87 per cent. 

Smelting. — Smelted at about 1200° C. for from 15 
to 18 minutes. The viscosity was rather low. Although 
the melting point of this enamel is low, it was difficult to 
drive off all the CO2. 

The Frit. — The frit was creamy and very opaque, 
but rather brittle. 

Milling. — Four hours with 7.87 per cent, tin oxide, 
4.5 per cen. Vallendar clay, and l^ per cent, magnesia. 

Acid Loss. — 0.0353 gram. This is entirely too high 
for a cooking utensil and places this ware last in the list 
as to its resistance to corrosion by acetic acid. 

Expansion and Contraction. — While heating this dish 
to redness, a few chips flew off and when plunged, red- 
hot, into cold water (Test 4) the enamel flaked off over 
quite a large surface, but only to the ground coat and 
even this was fairly well covered by the adhering cover 
coat. This ware stands fourth according to this test. 

Loss Under Hammer. — This was 0.56 gram, so that 
according to this test the enamel is very excellent indeed. 
It stands punishment by impact better than any of the 
rest. 

Appearance of Ware. — The opacity of this ware is 
very low, considering the fact that it contains 251/^ per 
cent, of tin oxide. It stands sixth when listed according 
to opacity. 

Cost. — The cost of this ware is $21.08 per hundred 
pounds. This is the most expensive of the wares, except 
one, and yet it stands sixth according to opacity and 
eighth when everything is considered. 

55 



Enamel IX 

Quartz 35.30% 0.670 NasO ^ f 9 4nfl «?in« 

Borax 20.50 0.062 K.0 L^^^ ^j^^sj 0:323 B.5. 

Cryolite 19.40 0.005 CaO ] r. r.oA f 

Feldspar 17.70 0.263 MgO J |^u.oo*r 

Magnesia 3.50 

Sodium carbonate 1.80 ORb = 3.4 ORa = 6.5 SiOVB^Os = 7.4 

Saltpeter 1.80 

Loss on Smelting. — 15.48 per cent. 

Smelting. — Smelted at about 1200° C. for from 15 to 
18 minutes. This enamel was difficult to pour from the 
crucible. The enamel was quite viscous and lumpy. 

The Frit. — The frit was very hard and, although 
quite opaque, was translucent in spots. 

Milling.^ — Three and a half hours with 10 per cent. 
Vallendar clay and 14 V^^ cent, magnesia. 

Acid Loss. — 0.0159 gram, or seventh in the list of 
ten enamels. 

Expansion and Contraction. — When plunged, red- 
hot, into cold water (Test 4) this enamel came off over a 
large surface on the outside and a small surface on the 
inside of the dish. The steel was laid bare in many places. 
In the list of wares, arranged according to their resistance 
to punishment by change of temperature, this enamel 
stands eighth, as it scaled slightly during Test 21/2 when 
water was boiled to dryness in it. 

Loss Under Hammer. — This was 1.42 grams, which 
is more than any of the other dishes lost, and places this 
enamel last in the list. 

Appearance of Ware. — This enamel is remarkable in 
its opacity, all of which comes from the cryolite and clay. 
It contains no tin oxide and stands eighth in the list ac- 
cording to opacity. 



^ Milling not given in original directions. 

56 



Cost. — The cost is but $2.87 per hundred pounds. 
With sufficient oxide added at the mill to bring this up to 
a remarkable standard, this enamel would cost about 
$5.50 per hundred pounds. Considering everything, this 
is the poorest enamel of the ten. 

Enamel X 

Feldspar 45.70% 0.841 Na^O 1 ("2.013 Si02 

Borax 32.00 0.142 K2O ^0.283 AbOa^ 0.625 B^Os 

Sodium carbonate 11.40 0.017 CaO J [ 0.227 SnOa 

Tin oxide 9.20 

Saltpeter 1.70 ORb = 3.2 ORa = 6.8 Si02/B208 = 3.2 

Loss on Smelting. — 21.33 per cent. 

Smelting. — Smelted at about 1050° C. for 20 minutes; 
this enamel became transparent, although it contains 9.2 
per cent, tin oxide. Its viscosity was medium. 

The Frit. — The frit was a colorless glass, compara- 
tively hard and quite tough. 

Milling. — Four and one-fourth hours with 6.4 per 
cent. Vallendar clay and l^ per cent, magnesia. 

Acid Loss. — 0.0119 gram, placing this enamel sixth 
in the list. 

Expansion and Contraction. — While heating to red- 
ness in the blast flame, the enamel bubbled slightly, and 
when plunged, red-hot, into cold water, came off to the 
steel over a small surface on the inside and a larger sur- 
face on the outside. This enamel stands fifth, according 
to this test. 

Loss Under Hammer. — This was 1.09 grams, which 
places this cover coat seventh in the list. 

Appearance of Ware. — Although this enamel con- 
tains 11.7 per cent, tin oxide, it stands last in opacity, be- 
ing nothing more nor less than a clear glass. 

Cost. — The cost of this enamel is $7.01 per hundred 
pounds. 

57 



Discussion 

MR. RANKIN: Mr. Landrum, I would like to ask 
if you have ever made any experiments in the line of sub- 
stituting sodium nitrate for potassium nitrate? 

MR. LANDRUM : I have made experiments on a 
small scale and a large scale. The substitution of sodium 
nitrate for potassium nitrate is successful only where you 
can make routine analyses of the sodium nitrate. Sodium 
nitrate takes up water from the air, and thus varies in 
strength. In the sheet steel enameling industry, the va- 
riation of water content will spoil the enamel unless this 
is taken into account. 

I worked in one place where they determine this very 
nicely by weighing about ten or fifteen pounds and then 
drying and reweighing it, thus getting results which were 
as accurate as taking a smaller sample and testing it in 
the laboratory. 

MR. STALEY: I wish to say that I consider this a 
very able paper. 

The Germans do not use the empirical formula in 
their enamel industries to any large extent. They publish 
their results in percentage of the various oxides. When 
it comes to fluorides, they publish their results in percent- 
age of the various fluorides. I think that is a fairly good 
way. In my own papers, I prefer to consider the melted 
weights of the various minerals; consider the feldspar, 
for instance, as feldspar rather than as split up into the 
oxides. The method I use is very similar to that of the 
Germans. Mr. Landrum advocates the use of empirical 
formulas in connection with batch weights. This diverg- 
ence in methods of calculation shows very nicely that, 
provided a man works in a systematic manner and has 
enough experience, he can get results from a variety of 
methods of calculation. 

Enamels III and X are two cases where there are 
high sodium and potassium oxides and practically no 

58 



other basic oxide. I believe that early in the history of 
this Society Mr. Burt gave the results of some experiments 
in which he showed that you can melt tin oxide and 
sodium carbonate, or tin oxide and potassium carbonate, 
together and get a clear glass. It is known that there 
are sodium stannates and potassium stannates in existence 
which are translucent. I think it is more plausible to say 
that in a material as basic as enamel the loss in opacity 
is due to the fact that the potash and soda are high rather 
than to attribute the poor opacity to any hypothetical 
effect that the alkaline earths have in preventing the tin 
from forming stannous silicate. I have always found that, 
with a given amount of tin oxide, when sodium and po- 
tassium run up the opacity decreases. To verify Mr. 
Landrum, I find that increasing calcium or barium oxide 
increases the opacity. To my mind this means simply 
that opacity was increased by decreasing the percentage 
of sodium and potassium. 

MR. PURDY: I would like to ask Mr. Landrum if 
it makes any difference in the power of tin oxide to pro- 
duce opacity, whether you frit it or use it raw? 

MR. LANDRUM : Yes, there is a very marked dif- 
ference. This has already been brought out in the Trans- 
actions. It never pays to put tin oxide in the smelt for 
opacity. 

I have found, however, that it is good practice to put 
a small amount of tin oxide in the smelt for gloss. In this 
case you get no opacity from the tin oxide. For maximum 
color, the tin oxide should be added at the mill. 



59 



THE NECESSITY OF COBALT OXIDE IN GROUND- 
COAT ENAMELS FOR SHEET STEEL* 

There has been a great deal of discussion recently 
in German ceramic literature over the function of the 
ground coat and especially as to the necessity of cobalt 
being present in such an enamel. As the durability of an 
enameled ware is primarily dependent upon the physical 
properties of this fundamental coating, it might be well 
to review what has been said upon the subject. 

In the Transactions of the American Ceramic Society, 
XI, p. 115, J. B. Shaw says that cobalt-containing grounds 
have the advantage that they change color during burn- 
ing, the iron taken up from the steel destroying the blue 
cobalt color. "The ground coat is considered well burnt 
when the blue color is no longer visible. It seems to be 
quite generally believed that CoO has a great affinity for 
iron and that a good ground coat cannot be made without 
using CoO." Shaw goes on to say that from his experi- 
ments along this line he feels perfectly safe in stating 
that this belief is ungrounded. 

About the only other time that this subject is men- 
tioned in the Transactions is by J. H. Coe, Volume XIII, 
p. 549, and he states that the value of cobalt oxide in the 
ground coat for cast iron is doubtful. 

Dr. Grunwald in his book "Enameling on Iron and 
Steel," p. 22, says: "Cobalt oxide possesses valuable 
physical characteristics which make it suitable for the 
preparation of ground (coat) enamels, for these derive 
the property that their coefficients of expansion are as 
near as possible the same as sheet iron." This is disputed 
by M. Mayer and B. Havas^ who find that ground coat 



♦Reprinted from the Transactions of the American Ceramic Society. Vol. XIV. 
(Paper read at Chicago 111., Meeting, March, 1912.) 
1 Chem. Ztg. Vol. XXXIII, p. 1314. 

60 



enamels have a much lower coefficient of expansion than 
that of sheet steel. 

Dr. Vondracek, in the Sprechsaal, 1909, No. 14, 
seems to have first propounded the theory of the function 
of cobalt in a ground-coat enamel which is most popular 
at present. He considers that the iron, at the melting 
temperature of the ground coat, is oxidized at the ex- 
pense of the cobalt oxide and that the latter, or rather 
the cobalt silicate, is changed to a compound of lower 
oxygen content, or is even reduced to the metal. As a 
result of this, the clean surface of the iron is attacked so 
that the enamel joins very intimately with the metal and 
the danger of the chipping off of the enamel coats is 
lessened. In another place. Dr. Vondracek, although he 
repeats that cobalt improves the adhesiveness of enamels, 
says : "I have, notwithstanding, often obtained a very ad- 
hesive ground-coat enamel without using cobalt oxide. "- 

Philip Eyer in his book "Die Eisenemailierung," pp. 
10-12, says: "The idea of adding cobalt oxide to the glaze 
so that it will go into combination with the iron is faulty, 
for a good, adherent ground-glaze can be prepared with- 
out the use of that oxide. However, the application of 
such a ground coat is impossible in practice." Also in 
writing of cast-iron enamels in the "Glashutte," Vol. 
XLI, pp. 737-8, 764-5, he says that cobalt and nickel are 
necessary as they form a weak alloy with the iron. 

C. Tostman, in the Keramische Rundschau, XIX, pp. 
5, 65 and 107, discusses this subject and emphasizes 
especially, what is, in the writer's opinion, the best argu- 
ment as to the necessity of cobalt in a ground coat. He 
agrees with Shaw that cobalt acts as an indicator for cor- 
rectly burning the enamel. He says in part: 

"Only in cobalt oxide grounds does a blue color appear on 
smelting. If one should discontinue the heating just at this point, 
it would not adhere firmly enough to the steel, even though it had 
already become molten and glass-like. One can also burn it so long 



2 See Chem. Ztg.. XXX, 575-7. 

61 



that the color becomes black. Now how is this (definite) color 
change, which is so markedly essential for a proper adhesion, to be 
explained? The only explanation I find for it is that the enamel has 
taken up the iron from the surface (of the black shape) in some 
form of oxidation." 

He goes on to state that while this oxygen might 
come from the air in the muffle, it is more probable that 
it is given up by the oxide of cobalt, which is in turn re- 
duced to metal. 'These small amounts of very finely di- 
vided metallic cobalt could then perhaps form a very 
porous alloy with the iron on the surface of the shape. 
To this, the enamel would be able to adhere firmly, while 
the silicate flux would take the place of the cobalt which 
alloyed with the iron." He gives as an argument that this 
oxygen is furnished to the iron by the cobalt and not 
from any other source, the fact that in ground coats, 
which are not colored by cobalt, "an exceedingly smaller 
change of color takes place during the burning." He 
also mentions the fact that the addition of borax to an 
enamel causes it to chip and the further addition of co- 
balt oxide seems to correct this. 

Dr. Bela Havas^ replies to Tostman that he agrees 
with him that the cobalt silicate in the ground coat is re- 
duced to a lower stage of oxidation and, as previously 
published by him in cooperation with M. Mayer,* this is 
indicated by the change of color of the enamel coating 
from blue to green. However, he states that it is im- 
probable that the reduction of the cobalt silicate at the 
temperatures involved would go far enough to produce 
metallic cobalt. 

The writer has no new theories to offer, but he is very 
strongly of the opinion that cobalt is a necessary ingredi- 
ent in a successful ground coat for two reasons, which 
have been given above : 

First, it is an excellent indicator which will inform 
the "burner" exactly the point at which his charge of 
ware is correctly burned. 

' Sprechsaal XLIV 72-3. 
*Ibid.. XLIII, 727-9. 

62 




Fig. 1 



Second,' whatever may be the reason, the fact re- 
mains that cobalt grounds adhere more firmly to the steel 
than those not containing this metal, and it is the opin- 
ion of the writer that any non-cobalt ground coat can be 
improved in its adhesive properties by the correct addi- 
tion of cobalt to its formula. 

To illustrate this a ground coat was prepared which 
is practically a transparent glaze. When it is coated on 
a piece of ware the bright steel surface shows through 
the glaze and makes this appear a very light colored 

coating (see Fig. I, 1). The composition is practically 
the same as that of the Mayer and Havas ground No. 1 
as given in the Sprechsaal, 1909, No. 34. 

M-H. Ground Coat Number One° 

Batch mix Graphic formula 

Feldspar 36.34% 0.642 NasO -i r 

Borax 35.64 O.O8O2K2O 2.256 Si02 

Quartz 14.38 0.243CaO Y 0.204 AbOa J 0.231 F2 

Soda 7.42 0.025 MnO 0.629 B2O3 

Fluorspar 5.34 0.010 CoO -' ^ 

Manganese oxide. 0.65 

Cobalt oxide 0.23 ORb 4.0, ORb 7.0, Si02/B20s 3.6 

Milled with 6 per cent, clay and 21/2 pei* cent, dis- 
solved borax. 

A cobalt ground coat has been prepared which has 
the same chemical composition except that 0.03 equiva- 
lent part of CaO has been replaced by 0.03 equivalent 
part of CoO (see Fig. I, 2). This enamel has been made 
as follows : 

Cobalt Ground Coat^ 

Batch mix Graphic formula 

Feldspar 36.42% 0.642 NasO 1 2.260 SiOa 

Borax 35.54 0.080 K2O I 

Quartz 14.38 0.213 CaO f 07203 AI2O3 J 0.628 BsQs 

Soda 7.42 0.040 CoO 1 

Fluorspar 4.64 0.025 MnO 1 0.201 Fa 

Manganese oxide. 0.65 

Cobalt oxide 0.95 ORb 4.0, ORa 7.0, Si02/B203 3.6 

® The same materials and method of manufacturing and a similar arrangement of 
data have been used as in "Comparison of Ten White Enamels for Sheet Steel," 
this volume. 

65 



Milled v/ith 6 per cent, clay and 21/2 Per cent, dis- 
solved borax. 

Each of these enamels has been coated with two 
v/hite cover coats and then tested under the hammer (see 
article on v/hite enamels), and it is to be noticed that the 
non-cobalt ground coat leaves the steel entirely bright 
and bare (see Fig. I, 3), while the one containing cobalt 
still adheres in concentric ridges (see Fig. I, 4). It is 
very evident that the cobalt must cause this extra ad- 
hesiveness. 

Discussion 

MR. LANDRUM : As an example of the reduction 
of a metal oxide (or silicate) in an enamel coating by the 
steel of the shape it may be interesting to examine a 
sample dish coated with the following enamel : 

0.451 NazO ] r0.886SiO2 

0.019 K2O 

0.123 CaO [ 0.111 Al=08 A 0.282 B^Os 

0.285 ZnO 

0.122 CuO ^0.123 F2 

Milled with 61/4 per cent. clay. 

This enamel when used as a cover coat (separated 
from the steel by a ground-coat enamel) is green but 
when applied directly to the steel becomes red through 
the reduction of the copper compound. It may be ob- 
served on the sample which has been dented in the test- 
ing machine that some of the copper compound has been 
reduced to the metal and that this is plated on the steel 
surface. 

MR. PURDY : You have tried oxides other than co- 
balt? Have you tried nickel, for instance? 

MR. LANDRUM : I have tried oxide of nickel and 
it works fairly well, but does not promote adhesiveness 
to as great a degree as does the oxide of cobalt. It is 
best used in combination with that oxide. 

66 



MR. PURDY: There is no actual oxygen for it to 
give up. 

MR. LANDRUM : We have nickelic and nickelous 
compounds, and the change may be from one to the other 
and not necessarily a change of the oxides ; then, too, the 
conclusion might be drawn that the reduction is to metal- 
lic nickel. In the case of the enamels under discussion, 
it is easy to see that the one containing cobalt (see vessel 
4 in illustration) does adhere to the steel after being 
dented while the one which does not contain cobalt (ves- 
sel 3) does not adhere but leaves the steel surface bright. 

PROF. STALEY: You will have to look at it with 
a microscope. 

MR. LANDRUM: I have examined this and other 
cobalt grounds under the microscope and have not been 
able to see any evidence of an alloy being present. The 
dark particles remaining after the dish is dented have a 
gloss that would lead one to think that they are particles 
of the glaze rather than of metal. Microscopic examina- 
tion is difficult as it is practically impossible to get a good 
cross section of an enameled steel sheet. 

PROF. STALEY : In other words, this alloy theory 
is used just because it fits in — because it is within reason? 

MR. LANDRUM: Yes, and even then there is a 
doubt that it is within reason at enameling temperatures. 

MR. PURDY: In our transactions I stated as my 
opinion that cobalt in the ground coat merely furnished 
a mechanical means of holding the enamel onto the iron. 
It is easy to enamel most metals directly, but very difficult 
to enamel iron. The cobalt is merely suspended in the 
ground coat furnishing the required easily enameled "go 
between." 

MR. LANDRUM : This may be true and would be 
a good explanation. There is an interaction between the 
iron and the enamel when you have cobalt present ; when 

67 



you do not have cobalt present there is no interaction. 
Sample 1 (see illustration), which is enameled vdth the 
non-cobalt ground coat, is nicely covered ; but under im- 
pact the enamel comes off, leaving the bright steel (see 
dish 3). Sample 2 is covered with the same enamel with 
1 per cent, of oxide of cobalt added, and when subjected 
to the same blow, adheres firmly in ridges, barely expos- 
ing the steel between them (see dish 4). Samples Nos. 
5 and 6 also show how the adhesiveness, under punish- 
ment by rapid changes of temperature, is promoted by 
the addition of oxide of cobalt. Both have been heated 
red hot and plunged into cold water. Number 5, whose 
fundamental coating contains no cobalt, peels off clean, 
to the steel, while 6, whose fundamental coating is the 
cobalt ground, exposes no steel at all. 

PROF. STALEY : I would like to have Mr. Landrum 
prove that there is an interaction between the ground 
coat and the iron when cobalt is present and no interaction 
when cobalt is absent. I would also like to see him de- 
monstrate the presence of a porous alloy between the 
enamel and iron. In regard to what Prof. Purdy has said, 
I would like to know on what evidence he bases his state- 
ment that cobalt is merely suspended in the ground coat 
and, furthermore, to explain the mechanics of just how 
such a suspension, if it should exist, would make a more 
tenacious ground coat. We have one fact, namely, that 
the addition of cobalt to a ground coat for sheet steel 
enamels makes it a better ground coat. This is admir- 
ably shown by Mr. Landrum's paper. Beyond this one 
fact, we can merely speculate until some one produces 
some evidence. 

MR. LANDRUM : We are merely speculating as to 
the "mechanics" of the action of the cobalt, but I believe 
that these samples show to the naked eye that there has 
been an interaction between the steel and the cobalt- 
containing enamel, and that there has not been such an 
interaction in the case of the non-cobalt enamel. It might 

68 



throw light on the subject to consider the fact that even 
a cobalt-containing ground coat will not adhere well to 
a steel surface unless that surface has been made rough, 
or porous or crystallized by pickling, sand-blasting, or 
annealing. It may be that the enamel simply sinks down 
into the pores of the steel, but the question is: Why 
should an enamel have to contain cobalt to do this? Now 
if some one has the facilities to make a cross-section of a 
piece of enameled steel, I would like to see it. Such a 
section might explain this matter. 



69 



METHODS OF ANALYSIS FOR ENAMEL AND 
ENAMEL RAW MATERIALS* 

Introduction. 1 The fact that practically nothing has 
been published on the above subject, and the remem- 
brance of the many long hours spent in digging out these 
methods and adapting them to enamels and enamel raw 
materials, has led the author to put them in this form for 
others who might use them. While he claims little origi- 
nality in the methods themselves, he does claim originality 
in the adaptations here given. Each and every one of 
these methods has been thoroughly tried out, either in 
the laboratory of the Columbian Enameling and Stamp- 
ing Company, at Terre Haute, Ind., or in the chemical 
laboratories of the University of Kansas. 

PART I. 

The Analysis of an Enamel 

The analysis of an enamel presents one of the most 
difficult and complicated problems with which the an- 
alyst comes in contact. An enamel is generally an in- 
-soluble silicate containing besides silica, iron, alumina, 
calcium, magnesium and the alkalies, generally boron, 
fluorine, manganese, cobalt, antimony and tin, and some- 
times phosphorus and lead. Before attempting the quan- 
titative analysis of any enamel a thorough qualitative 
analysis should be run, and this will enable one to choose 



* Reprinted from Vol. XII, page 144, Transactions of American Ceramic Society. (Read 
at Pittsburgh Meeting, February, 1910. 

1 This paper was prepared as a thesis for the master's degree at Rose Polytechnic 
Institute. The author desires to render thanks to Dr. W. A. Noyes and Dr. John 
White, his former instructors, for advice freely given, and to Dr. E. H. S. Bailey 
and Dr. H. P. Cady for suggestions offered. Methods, especially from the following 
sources, have been freely used, and adapted to the specific uses herein described ; 
Treadwell and Hall's "Analytical Chemistry" ; Classen's "Ausgewahlte Methoden der 
Analytischen Chemie" ; Sutton's "Volumetric Analysis" ; Lunge and Keane's "'Techni- 
cal Methods of Chemical Analysis" ; "Methods of Agricultural Analysis" (Bui. 107. 
U. S. Dep't of Agric.) ; Hillebrand's "Analysis of Silicate Rocks" (U. S. Geol. Survey 
Bui. 305) ; and the files of the Journals of the various Chemical Societies. 

70 



a quantitative separation. One of the most important 
aids to a correct analysis is a thorough grinding. The 
sample should be ground to an almost impalpable powder, 
and every conceivable precaution for accuracy taken. 

The analysis of a sample of enamel to be taken from 
a piece of ware involves an extra difficulty. The coating 
of enamel almost always consists of two or more layers — • 
the lower a large ground coat, and the upper ones white 
or colored enamels. For an illuminating analysis these 
must be separated. The author has found the following 
method of V. de Luyeres^ good for doing this: The sur- 
face is scratched lightly with a piece of emery cloth or a 
file, and a coating of gum acacia or glue is applied. The 
vessel is placed in an air-bath and heated. The glue on 
hardening generally carries with it some of the outer 
coat. The glue or gum is then broken off, dissolved in 
water and the enamel pieces collected on a niter paper. 
Some obstinate enamels require painstaking methods, 
such as chipping off with a chisel and separating the dif- 
ferent coats — which always vary somewhat in color — by 
picking out and sorting, using a pair of forceps. A large 
reading glass will be useful in making these separations. 
Any iron from the vessel which may adhere to the enamel 
may be removed by means of a magnet after the sample 
is ground. 

Analysis of an Eisamel Contaming Fluorine 

In an enamel containing fluorine the usual methods 
for silicates cannot be used, as silicon-tetra-fluoride would 
be volatilized in the evaporation with hydrochloric acid 
for the separation of the silica. 

Fluorine. One gram sample is very finely ground, 
slowly fused with two grams each of potassium carbonate 
and sodium carbonate. The melt should be kept in quiet 
fusion over as low a flame as possible for one hour. The 
melt is transferred, (after cooling quickly by giving the 



1 Compte Rendus 8, p. 480. 

71 



crucible a gyratory motion while held in the tongs, caus- 
ing the melt to cling to the sides instead of forming a 
solid cake in the bottom), to a platinum dish where it is 
covered with a watch glass and boiled vigorously with 
one hundred cc. of water. The residue is filtered oflf and 
is saved for the determination of the metallic oxides and 
the silica. 

The covered solution is digested on a steam bath for 
an hour with several grams of ammonium carbonate, and 
on cooling more carbonate is added and the solution is 
allowed to stand for twelve hours. The precipitate of 
silica, alumina, etc., is filtered off, washed with ammo- 
nium carbonate water and is saved for further determi- 
,nations. 

The solution containing all the fluorine and traces of 
silica, phosphate, etc., is evaporated until gummy, then 
diluted with water and neutralized as follows: Phe- 
nolphthalein is added, and nitric acid (double normal) 
drop by drop until solution is colorless. 

The solution is boiled and the red color which reap- 
pears is again discharged with nitric acid, boiled again 
and neutralized again until one cc. of acid will discharge 
the color. 

The last traces of silica, etc., are now removed, as 
recommended by F. Seemann (Zeit. Anal. Chem. 44, p. 
343), by the addition of 20 cc. of Schaffgotsch solution. 
This solution is made as follows: 250 grams of ammonium 
carbonate are dissolved in 180 cc. of ammonia (0.92 sp. 
gr.) and the solution is made up to one liter. To the cold 
solution 20 grams of freshly precipitated mercuric oxide 
are added and the solution is vigorously shaken until the 
mercuric oxide is dissolved. 

The precipitate caused by the Schaffgotsch solution 
is filtered off and saved, and the solution is evaporated 
to dryness and the residue taken up with water. 

72 



Any phosphorus from the bone ash used in some 
enamels, and chromium which may be present, are re- 
moved from this alkaline solution by adding silver nitrate 
in excess. Phosphate, chromate and carbonate of silver 
are here thrown down and may be determined' if desired. 

The excess of silver is removed from the solution by 
sodium chloride, and one cc. double normal sodium car- 
bonate solution is added to the filtrate, and the fluorine 
is precipitated by boiling with a large excess of calcium- 
chloride solution. 

The precipitate, consisting of a mixture of calcium 
carbonate and fluoride, is collected on a blue ribbon filter 
paper and is washed, dried, ignited at low red heat, sep- 
arated from the filter paper, and the residue with the ash 
of the paper is treated with dilute acetic acid until carbon 
dioxide is no longer given off on heating. The liquid is 
then evaporated to dryness, the residue taken up with hot 
water (slightly acidified with acetic acid) filtered, dried 
and gently ignited and weighed as CaFo. This may be 
checked by heating with sulfuric acid, driving off all the 
excess of acid and reweighing as CaSO^. This method 
gives results for the amount of fluorine checking within 
0.2%, but which are generally from 2% to 4% low. 

Silica. For the estimation of silica and the metallic 
oxides, first the precipitate from the Schaffgotsch mer- 
curic oxide solution is ignited to drive off the mercuric 
oxide, and the silica left is weighed. The residue from 
the original melt, together with the precipitate obtained 
by ammonium carbonate (after the drying and removal 
from the filter paper whose ash is added) are then dis- 
solved in hydrochloric acid. The solution is evaporated 
to dryness and moistened with hydrochloric acid. It is 
diluted with water and the silica is filtered off, weighed, 
and this with that previously obtained is the total silica. 

Iron, Alumina and Manganese. The solution from 
the silica is raised to boiling and the iron and aluminum 

73 



are precipitated as hydroxides. Then 5 cc. of bromine 
water is added and the boiling continued for five minutes. 
The precipitate is dried on filter-paper and ignited separ- 
ately from it in a weighed platinum crucible, to which 
the ash of the filter-paper is afterwards added. The pre- 
cipitate consists of AI2O3, FeaOg, and Mn^Og, and is 
weighed as such. It is then fused with fifteen times its 
weight of potassium pyrosulfate over a low flame for 
three hours with the crucible covered. The crucible, con- 
tents and cover are placed in a beaker and dilute sulfuric 
acid (10:1) is added. By warming and continued shak- 
ing of liquid complete solution may be obtained. It is 
then drawn through a Jones Reductor to change all the 
iron to ferrous and titrated with N/10 potassium perman- 
ganate solution. The iron is calculated to Fe^O^ and the 
alumina determined by difference. 

If manganese is present it is determined in a separate 
sample in a method given later and is subtracted from the 
iron in the above. In white enamels containing only a 
trace of iron the manganese may be determined in the 
solution from the pyrosulfate fusion. A freshly prepared 
solution of potassium ferrocyanide is added to oxidize 
the manganese, then the solution is made alkaline with 
sodium hydroxide solution and the manganese-dioxide 
thus formed is filtered off. The solution is then made 
acid and the ferrocyanide is titrated with N/10 potassium 
permanganate solution. (1 cc. KMnO^ = 0.00435 gram 
MnO.) 

Calcmm Oxide, The filtrate from the iron and 
alumina is raised to boiling, treated with boiling ammon- 
ium oxalate solution and digested on water bath until 
precipitate readily and quickly settles after being stirred. 
The calcium oxalate is now filtered off and ignited wet in 
platinum to constant weight over a strong blast. 

Magnesium Oxide. The solution is evaporated to 
dryness and the residue ignited to remove ammonium 
salts. The residue is treated with a few drops of hydro- 

74 



chloric acid and taken up with boiling water and filtered 
from the carbonaceous residue. To the boiling solution 
is added drop by drop a solution of sodium ammonium 
phosphate and is allowed to cool. Half as much concen- 
trated ammonium hydroxide is added as there is solution 
and it is allowed to stand over night. The precipitate is 
collected on a filter, washed with 3% ammonia water, 
dried in oven and ignited separate from the filter. The 
heat is applied gently at first and finally with the highest 
heat of a good Bunsen burner. It is then weighed as 
Mg,P,0,. 

1 gram Mg2P£07 = .3625 grams MgO 

The alkalies are determined by the method of J. 
Lawrence Smith from a gram sample finely powdered. 
This method is standard and need not be given here. 

Separation and Determination of Antimony, Tin, 
Manganese and Cobalt in Enamel 

Decomposition. Two grams finely powdered sample 
are transferred to a platinum dish, and after moistening 
with a little water, pure hydrofluoric acid is added and 
the whole is mixed with a platinum spatula. The dish is 
digested on steam bath for five hours covered with plati- 
num cover (a larger platinum dish may be used for cover 
if no other is at hand). After the decomposition is com- 
plete the solution is evaporated to dryness on steam bath. 
The residue is moistened with enough dilute sulfuric acid 
(1:1) to make a thin paste, and evaporated as far as 
possible on a steam bath and then on a hot plate, all the 
time being covered to prevent spirting. As soon as fumes 
of sulfuric anhydride cease to be evolved the cover is 
strongly heated until fumes cease to be driven off, when 
it is removed. The contents are heated by bringing the 
dish to dull redness directly over a Bunsen burner. The 
sulfates thus formed are moistened with strong hydro- 
chloric acid, a little hot water is added and the solution 
boiled with repeated additions of acid and water until 

75 



completely in solution. In some enamels — especially 
those with high melting points — the stannic oxide remains 
undissolved, and a fusion of the residue with sulfur and 
sodium carbonate as given later under "The Analysis of 
Oxide of Tin" may be necessary. 

Treatment with H^S. The solution containing at 
least 30 cc. double normal hydrochloric acid is transferred 
to a 500 cc. Ehrlenmeyer flask fitted with a double bored 
stopper. Through one of the holes a right-angled piece 
of glass tubing is introduced that just reaches to the lower 
edge of the stopper, while through another hole another 
right-angled glass tube is fixed so that it almost reaches 
the bottom of the flask. 

A Kipp HoS generator is connected to the longer tube 
and HgS is passed through for half an hour and the solu- 
tion is let stand for another half an hour, after which the 
sulfides of antimony and tin are transferred to a filter 
paper and the solution is kept for the determination of 
manganese and cobalt. 

Antimony and Tin. The precipitated sulfides are 
dissolved in a solution of potassium polysulfide — if any 
lead or copper is present it will remain undissolved and 
may be determined separately — by pouring this succes- 
sively through the filter into a 300 cc. Jena beaker, and 
finally washing with water containing a small amount of 
potassium polysulfide. 

Antimony. The antimony and tin in this solution 
are separated by F. W. Clark's method as modified by 
F. Henz% as follows: 

To the solution in the Jena beaker 6 grams caustic 
potash and 3 grams tartaric acid are added. To this 
mixture twice as much 30 per cent, hydrogen peroxide is 
added as is necessary to completely decolorize the solu- 
tion, and the latter is now heated to boiling and kept there 



iTreadwell, Vol. II, p. 188. 

76 



until the evolution of oxygen is over, in order to oxidize 
the thiosulphate formed. All of the excess of peroxide 
cannot be removed successfully at this point. The solution 
is cooled somewhat, the beaker covered with a watch- 
glass, and a hot solution of 15 grams pure recrystallized 
oxalic acid is cautiously added (5 gms. for 0.1 gm. of the 
mixed metals). This causes the evolution of considerable 
carbon dioxide. Now, in order to completely remove the 
excess of hydrogen peroxide the solution is boiled vigor- 
ously for ten minutes. The volume of the liquid should 
amount to from 80 to 100 cc. After this a rapid stream 
of hydrogen sulfide is conducted into the boiling solution, 
and for some time there will be no precipitation, but only 
a white turbidity formed. At the end of five or ten min- 
utes the solution becomes orange colored and the anti- 
mony begins to precipitate, and from this point the time is 
taken. At the end of fifteen minutes the solution is di- 
luted with hot water to a volume of 250 cc, at the end of 
another fifteen minutes the flame is removed, and ten 
minutes later the current of hydrogen sulfide is stopped. 
The precipitated antimony pentasulfide is filtered off 
through a Gooch crucible which, before weighing and 
after drying, has been heated in a stream of carbon di- 
oxide at 300° C. for at least one hour. The precipitate 
is washed twice by decantation with 1 per cent, oxalic 
acid and twice with very dilute acetic acid before bring- 
ing it in the crucible. Both of these wash liquids should 
be boiling hot and saturated with hydrogen sulfide. 

The crucible is heated in a current of carbon dioxide 
(free from air) to constant weight, and its contents 
weighed as SboSg. 

The filtrate is evaporated to a volume of about 225 
cc, transferred to a weighed unpolished platinum dish, 
and electrolyzed at 60° to 80° C. with a current of 0.2 to 
0.3 ampere (corresponding to 2 to 3 volts). For very 
small amounts of tin, a current of not over 0.2 ampere 
should be used. At the end of six hours 8 cc. of sulfuric 

77 



acid (1:1) are added, and at the end of twenty-four 
hours the solution is transferred to another dish. The 
deposited tin has a beautiful appearance, similar to silver. 

Tin. The plated tin is washed thoroughly with water 
and the dish is dried in an air oven at 110° and weighed. 

The solution containing the cobalt and manganese is 
boiled until free from HoS. The iron is oxidized back to 
the ferric state by the addition of bromine water and 
boiling until the excess of the latter is expelled. Ten cc. 
double normal ammonium chloride is added and the iron 
and alumina are precipitated by the addition of ammonia 
and are filtered off. (The iron alumina may be deter- 
mined from this precipitate if desired.) 

The solution still containing the manganese and co- 
balt is transferred to an Ehrlenmeyer flask fitted for pass- 
ing in HoS, as before described, and 3 cc. strong ammonia 
is added. HgS is passed through for some time, and after 
precipitation ceases 3 cc. more of ammonia are added and 
the flask is filled to the neck (300 cc. flask), is corked and 
set aside for twelve hours at least. The precipitate is 
collected and washed on a small filter with water contain- 
ing ammonium chloride and sulfide. 

Manganese. The manganese is extracted from the 
precipitate on the filter by pouring through it strong HjS 
water acidified with 1-5 its volume hydrochloric acid (sp. 
gr. 1.11) . This solution from the extraction is evaporated 
to dryness, ammonium salts are destroyed by evaporation 
with a few drops of sodium carbonate solution, hydro- 
chloric acid and a drop of sulfurous acid are added to 
decompose excess of carbonate and to dissolve the pre- 
cipitated manganese, and the latter is reprecipitated at 
boiling heat by sodium carbonate after evaporating off 
the hydrochloric acid. The manganese is weighed as 
MngO^ and calculated to MnOo, in which form it is prob- 
ably present in the enamel. 

The residue of cobalt sulfide left after extracting the 
manganese is burned in a porcelain crucible, dissolved in 

78 



aqua regia, and evaporated with hydrochloric acid; the 
platinum — and copper if any is present — are thrown 
down by heating and passing in hydrogen sulfide. The 
filtrate from the platinum and copper is made ammonia- 
cal, and cobalt is thrown down by hydrogen sulfide. This 
is filtered off and washed with water containing ammo- 
nium sulfide. This is either ignited and weighed as oxide 
or more accurately determined by dissolving in an ammo- 
niacal solution of ammonium sulfate, containing 10 grams 
of ammonium sulfate and 40 cc. of concentrated ammonia 
for each 0.3 grams of cobalt, and electrolyzing in a 
weighed platinum dish at room temperature with a cur- 
rent of 0.5 to 1.5 ampere, and an electromotive force of 
2.8 to 3.3 volts. The electrolysis is finished in three hours. 
The circuit is broken and the liquid poured off, and the 
platinum dish is washed with water, then with absolute 
alcohol (distilled one hour) and finally with ether, al- 
lowed to dry in oven at 95° for one minute and then 
weighed. The metallic cobalt is calculated as CoO, in 
which form it is present in the enamel. 

The Determination of Boric Anhydride in Enamel 

The boron is determined in a separate sample of 
about 0.3 grams. This finely pulverized sample is fused 
with three grams sodium carbonate for fifteen minutes, 
is taken up with thirty cc. dilute hydrochloric acid and a 
few drops of nitric acid. The melt is heated in a 250 cc. 
round-bottomed flask almost to boiling, and dry precipi- 
tated calcium carbonate is added in moderate excess. The 
solution is boiled in the flask after it has been connected 
with a six-inch worm reflux condenser. The precipitate 
is filtered on an 8 cm. Buchner^ funnel, and is washed 
several times with hot water, taking care that the total 
volume of the liquid does not exceed 100 cc. 

The filtrate is returned to the flask, a pinch of cal- 
cium carbonate is added and the solution is heated to 



1 See Method of Wherry and Chapin, Jr., Am. Chem. Soc. 30, p. 1688, for Deter- 
mination of Boron in Silicates. 

79 



boiling to remove the free carbon dioxide. This is best 
done by connecting the flask to a suction pump, and the 
suction is applied during boiling. The solution is cooled 
to ordinary temperature, filtered if the precipitate has a 
red color, and four or five drops of phenolphthalein is 
added and N/10 sodium hydroxide solution is run in 
slowly until liquid has a strongly pink color. A gram of 
mannite (or 150 cc. of neutral glycerol) is added, where- 
upon the pink color will disappear. Continue to run in 
N/10 sodium hydroxide until end point is reached. Add 
more mannite or glycerol and if necessary more alkali, 
until a permanent pink color is obtained. 

1 cc. N/IO Sodium Hydroxide = .0035 g. B20« 

Lead. The enamel for cooking utensils should never 
contain lead. To determine whether a cooking utensil 
contains lead, E. Adam gives the following simple quali- 
tative method: A small piece of filter paper moistened 
with hydrofluoric acid is placed upon the enamel and al- 
lowed to remain for some minutes; the paper, together 
with any pasty mass adhering to the enamel, is then 
washed off into a small platinum basin, diluted with 
water, and tested for lead by passing HoS through the 
solution. 

J. Grunwald (Oesterr. Chem. Ztg. 8, p. 46) gives an- 
other quick test for lead : Wet small portion of surface 
with HNOg (cone.) and heat until acid is evaporated. 
Add several drops of water and a few drops 10% potas- 
sium iodide solution, and if even a trace of lead is present 
yellow lead-iodide will be produced. 

Determination of Phosphoric Anhydride in Enamel 

Enamels containing bone ash to give opaqueness are 
analyzed for PsOg as follows: 

To a gram sample of very finely pulverized enamel 
in a platinum crucible one cc. of sulfuric acid is added 
and the crucible is filled half full (about ten cc. are re- 

80 



quired) with hydrofluoric acid. The crucible is heated 
on the water bath until most of the solution is evaporated 
and then gently on a hot plate to remove all the fluorine 
as silicon-tetra-fluoride and as hydrofluoric acid, but no 
sulfuric acid fumes should evolve, as PgOg is volatile. The 
residue is dissolved in nitric acid and taken to dryness, 
moistened with nitric acid, diluted with water, filtered 
and washed with a very little water. 

Add aqueous ammonia to the solution from above 
until the precipitate of calcium phosphate first produced 
just fails to redissolve, and then dissolve this by adding a 
few drops of nitric acid. Warm the solution to about 
70° C. and add 50 cc. ammonium molybdate solution (70g. 
M0O3 per liter). Allow the mixture to digest at 50° for 
twelve hours. Filter off precipitate washing by decanta- 
tion with a solution of ammonium nitrate made acid with 
nitric acid. 

The precipitate on the filter is dissolved by pouring 
through it dilute ammonia solution (one volume of 0.96 
sp. gr. ammonia to three volumes of water) . 

The solution is received in the beaker containing the 
bulk of the precipitate, all of which is dissolved in the 
ammonia solution. 

An excess of magnesium ammonium chloride ("mag- 
nesia mixture") solution is added very slowly and with 
constant stirring. Let solution stand over night. Decant 
clear solution through a filter and wash by decantation 
with ammonia water (1: 3). Dissolve the precipitate by 
pouring a little hydrochloric acid (sp. gr. 1.12) through 
the filter, allowing the acid solution to run into the beaker 
containing most of the precipitate. When all the precipi- 
tate on the filter and in the beaker is dissolved wash the 
filter paper with a little hot water. To the solution add 
2 cc. magnesia mixture and then strong ammonia, drop by 
drop, with constant stirring until distinctly ammoniacal. 
Stir several minutes, then add strong ammonia equal to 
one-third of the liquid, let stand two hours and filter off 

81 



the precipitate of magnesium ammonium phosphate. 
Wash with dilute ammonia water, dry the precipitate, 
ignite separately from the filter, first at low temperature 
and gradually raise to full blast. Weigh precipitate as 
MgoPaO^ and calculate as P2O5 in sample. 



PART li. 

THE ANALYSIS OF ENAMEL RAW MATERIALS 
The Analysis of Borax 

Sampling, A handful is taken from the middle of 
every tenth bag as it is unloaded. The sample from the 
entire car-load is then quartered down to two pounds. 
This is crushed so that it will pass through a forty mesh 
sieve. This is futher quartered to about thirty grams. 
Sample is then accurately weighed and thoroughly dis- 
solved in about 600 cc. hot — not boiling — water in a liter 
volumetric flask, and when cool is diluted to the mark. 
One hundred cc. of this, representing one-tenth of the 
sample, is then taken for analysis. 

Detenninatioia of Sodium Oxide and Boric Acid. Ti- 
trate with normal sulfuric or hydrochloric acid solution, 
using methyl orange as indicator. 

Number cubic centimeters Normal Acid X .031 = g, 
NagO. The solution is now boiled, covered v/ith a watch 
glass to expel COo, and on cooling may turn pink. Add 
normal KOH solution (a drop will do) to bring back yel- 
low color. At this stage all the boric acid exists in a free 
state. 
(2Na"+B407- -) +H!=0+ (2H^+2C1-) = (2Na^+2Cl-) +4 (H*+4B03-) 

Add as much neutral glycerol as there is solution 
(about 150 cc.) and titrate with normal potassium hy- 
droxide, using phenolphthalein as indicator. If end is 
not distinct add more glycerol and more indicator. The 
addition of glycerol causes the boric acid to become more 

82 



dissociated, probably due to the formation of boroglyceric 
acid, and the end-point is quite distinct. The following 
equation represents essentially what takes place : 

(4H^+4BO^) + (4K*-I-40H-) = (4K*+4BO^) +4H2O 
1 cc. normal KOH solution — .035 g. BaO* 

If the analysis gives more NaoO than is required to 
calculate all the B2O3 to Na^B^OT, the remainder comes 
from sodium carbonate with which it has been adulte- 
rated. 

Calculation of Results. The analysis of the borax is 
very important, as many times samples are adulterated, 
and even when not adulterated seldom contain exactly 
enough water to give the formula NagB^O/ IOH2O. It is 
.necessary to know the strength of the borax not only to 
buy intelligently, but also so that each and every mix of 
enamel v/ill contain the same amount of borax. 

It is customary to calculate from the percent of B2O3 
in sample the percent strength of the sample as Nag 
B.O/IOH^O. 

%B203 X 2.7307 = %Na2B407 • IOH2O 

When the sample has dehydrated of course this will 
run over 100%, and thus the correspondingly fewer 
pounds of borax may be used in the mix of enamel. 

Moisture. On account of the large amount of water 
of crystallization in borax it is difficult to determine the 
moisture directly, therefore it is calculated by subtracting 
the % Na^B.O/ lOH.O and the % Na^COs (if any is 
present) from 100%. 

The Analysis of Ground Sand, Flint and Quartz 

Fineness. These, as are most of the raw materials 
used in the enamel, are tested for fineness. One kilogram 
is weighed on balance sensitive to 1/10 gram and is 
shaken on a 100 mesh sieve. The material remaining on 

83 



the sieve is v>^eighed. This is then shaken on an 80 mesh 
sieve and the residue weighed. From this is calculated 
percent through 100 mesh and percent through 80 mesh. 
The finer the material the better it is for use in making 
enamel. 

An analysis for SiOo, Fe.Og and MgO is run when a 
new material is being tried, but generally only the SiOj 
and FeoOg are determined. In this case the acid solution 
from the silica is reduced by passing through a Jones 
Reductor and is titrated with N/10 potassium bichromate. 

Preparation for Analysis. The material is carefully 
sampled by quartering down to several grams. This is 
ground in an agate mortar to pass completely through a 
hundred mesh sieve. This grinding is generally done by 
hand but an enameling works laboratory should be 
equipped with a McKenna Grinder, (manufactured by 
McKenna Bros. Brass Company, Ltd., of Pittsburgh), in 
which the material can be ground in an agate mortar by 
power. 

The method followed for the analysis of flint and 
other forms of silica as well as clays and feldspars, is in 
all essentials, a well known method given by Hillebrand 
in analysis of silicate rocks, U. S. Geological Survey Bull. 
305, and for reasons of space this method will not be 
given here. 

The Determination of Titanium in Enamels, Clays and 
Silicate Minerals 

Titanium is determined after the determination of 
the iron by titrating with permanganate. This solution 
(after titrating) is diluted to 1000 cc. and is treated with 
hydrogen peroxide and the titanium determined by A. 
Weller's Colorimetric Method,^ from one-half the solution. 

This determination depends upon the fact that acid 
solutions of titanium sulphate are colored intensely yel- 



1 Berichte 15, p. 25-98. 

84 



low when treated with hydrogen peroxide; the yellow 
color increases with the amount of titanium present and 
is not altered by an excess of hydrogen peroxide. On the 
other hand, inaccurate results are obtained in the pres- 
ence of hydro-fluoric acid (Hillebrand) ; consequently it 
is not permissible to use hydrogen peroxide for this de- 
termination which has been prepared from barium per- 
oxide by means of hydrofluosilicic acid. Furthermore, 
chromic, vanadic, and molybdic acids must not be present, 
since they also give colorations with hydrogen peroxide. 
The presence of small amounts of iron do not affect the 
reaction, but large amounts of iron cause trouble on ac- 
count of the color of the iron solution. If, however, phos- 
phoric acid is added to the colored ferric solution it be- 
comes decolorized, and from such a solution the determi- 
nation of titanium offers no difficulty. The solution in 
which the titanium is to be determined must contain at 
least 5 per cent, of sulfuric acid; an excess does not in- 
fluence the reaction. The reaction is so delicate that 
0.00005 gm. of TiOa present as sulphate in 50 cc. of solu- 
tion give a distinctly visible yellow coloration. 

For this determination a standard solution of titan- 
ium sulfate is required. This can be prepared by taking 
0.6000 gm. of potassium titanic fluoride which has been 
several times recrystallized and gently ignited (corres- 
ponding to 0.2 gm. of TiO,). This is treated in a platinum 
crucible several times with a little water and concentrated 
sulfuric acid, expelling the excess of acid by gentle igni- 
tion, finally dissolving in a little concentrated sulfuric 
acid and diluting with 5 per cent, sulfuric acid to 100 cc. 
One cubic centimeter of this solution corresponds to 0.002 
gm. TiO^. 

The determination proper is carried out in the same 
way as the colorimetric determination of ammonium in 
the sanitary analysis of water. 

50 cc. of the solution which has been brought to a 
definite and accurately measured volume is placed in a 

85 



Nessler tube beside a series of other tubes, each contain- 
ing a knovv^n amount of the standard titanium solution, 
filled up to the mark with water and each treated with 

2 cc. of 3 per cent, hydrogen peroxide^ (free from hydro- 
fluoric acid). The color of the solution in question is 
compared with the standards. This method is only suit- 
able for the estimation of small amounts of titanium, as 
the shades of strongly colored solutions cannot be com- 
pared accurately. 

The Analysis of Oxide of Tin 

Stannic Oxide. As this is one of the most important 
and most expensive of the raw materials used in enamel- 
ing, an analysis is very necessary. The oxide is bought 
to contain not less than 99.5% SnO,, and in this the im- 
purities will consist of minute traces only of other ma- 
terials. For an oxide of this kind from .2 to .3 of a gram 
of the sample is placed in a porcelain casserole, about 
10 cc. of C. P. nitric acid of a sp. gr. 1.2 is added and the 
solution is slowly evaporated to a volume of about 2 or 

3 cc, diluted to about 30 or 40 cc. of water, kept warm 
for about a half hour, filtered on a small blue-ribbon filter 
paper, and washed with warm water, slightly acidulated 
with nitric acid, being careful to avoid letting the preci- 
pitate creep up. 

The precipitate is dried on filter paper in the funnel 
by placing in a hot air bath. The dried tin oxide is then 
removed as completely as possible from the filter paper 
and the paper is ignited in a porcelain crucible, being 
sure that there is an excess of air so that there will be no 
metallic tin reduced. 

The balance of oxide of tin is now added to the cru- 
cible and the whole is moistened with a drop of nitric 
acid, the temperature under the crucible is gradually 
raised until it comes to a bright red heat over the blast 
flame. 



^ The hydrogen peroxide solution is prepared shortly before using by dissolving 
commercial potassium percarbonate in dilute sulfuric acid. 

86 



This method gives results which check within one- 
tenth of a per cent. 

Some brands of oxide of tin on the market contain a 
number of impurities in considerable quantities. Lead, 
iron, silica, Sodium chloride, sodium sulfate and water 
are the most common of these. These are determined as 
follows: 

Direct Method. Methods for the direct determina- 
tion of the tin have proven quite unsatisfactory but the 
following, with very careful manipulation, yields results 
checking within 0.2% : 

Five-tenths grams of oxide is mixed in a porcelain 
crucible with 3 grams each of powdered sulfur and dry 
carbonate of soda, which both of course must be C. P., 
especially free of metals and earths. The covered cruci- 
ble is heated for about an hour at low heat first, and later 
at the heat of a regular Bunsen burner ; then let cool with- 
out lifting the cover. The cold mass is dissolved in water, 
filtered and washed with water to which was added a 
little sulfide of ammonia ; the residue is brought back in 
the crucible and the melting process repeated, of which 
the solution is filtered to the first melting. The sulfide tin 
solution then is acidulated with hydrochloric acid and the 
precipitated sulfide of tin is allowed to settle clearly, after 
which it is filtered and washed with sulfide of hydrogen 
water. 

The wet precipitate of sulfide of tin is transferred 
to an Ehrlenmeyer flask and treated with dilute hydro- 
chloric acid and bromine until completely dissolved, at a 
low heat. The filter left after the solution is filtered off 
is washed and the SnCL solution is precipitated with am- 
monia and a little nitrate of ammonia, allowed to settle, 
filtered and washed. After drying, the precipitate is 
ignited at white heat and is weighed as SnOa. 

Reduction Method. When the qualitative analysis 
shows no metal other than tin present, a very satisfactory 

87 



method is to reduce a weighed quantity of the sample in 
a Rose crucible by heating to redness in a stream of hy- 
drogen. The silica, if any is present, may be determined 
by dissolving out the tin with hydrochloric acid and 
weighing the residue. 

Combined Water. In oxides which are prepared by 
certain precipitation methods, the combined water runs 
as high as ten per cent. To determine this, a two gram 
sample is heated in a porcelain crucible at a white heat 
to constant weight. The loss is combined water. 

Lead. The lead is determined from the nitric acid 
solution and washings from the tin oxide determination 
by precipitation as the sulfate. 

Iron. Digest about one gram with twenty-five cc. 
of concentrated hydrochloric acid. As much water is 
added and the solution is boiled for five minutes. The 
residue is filtered off and about a cubic centimeter of con- 
centrated sulfuric acid is added and the solution is evap- 
orated until the sulfuric fumes come off. The solution is 
diluted, passed through a Jones Reductor and titrated 
with N/10 potassium permanganate solution. 

Soluble Salts. About two grams of the sample is 
boiled with water for thirty minutes. The residue is fil- 
tered on a blue-ribbon paper and is dried in an air bath. 
It is then separated as completely from the paper as is 
possible. The paper is burned in a platinum crucible. A 
drop of nitric acid is added and the crucible is raised to 
bright red. The whole of the residue is now added and 
heated to white heat for some time. (If there was com- 
bined water present in the sample of course it will be 
driven off, and this must be taken into calculation). 

The loss in weight (minus the above correction) is 
the soluble salts — usually sodium chloride and sulfate. 

If desired these may be determined definitely by 
usual methods. (Titration of an aliquot part with N/10 
silver nitrate solution for the chloride and precipitation of 



the sulfate as barium sulfate in another aliquot part 
slightly acidifies with nitric acid.) 

Silica. To the residue in the platinum crucible from 
the above determination several drops of sulfuric acid are 
added, and the crucible is filled within a quarter of an 
inch of the rim with pure hydrofluoric acid. This is 
volatilized, carrying with it any of the silica as hydrofluo- 
silicic acid. Loss of weight = SiOj. 

The Analysis of Pyrolusite 

Pyrolusite has two uses in enamel, first as an oxidiz- 
ing agent, and second to give an amethyst color to the 
enamel frit. Its grading, however, is generally made on 
its oxidizing value. This is found as follows : 

Manganese Dioxide. A sample is carefully taken 
from each barrel of the shipment, and after quartering 
down to about ten grams is ground so as to pass through 
a 200 mesh sieve. (It is better to test this by seeing if 
any grit can be detected when the powder is placed be- 
tween the teeth.) The sample is dried, spread out on a 
watch glass, at 110° for one hour, transferred to a stop- 
pered weighing tube, and after weighing, about one-half 
gram is transferred into a 250 cc. Ehrlenmeyer flask. For 
each gram of sample weighed out add at least 0.9 grams 
pure, tested oxalic acid (H2C2O4 2H2O) weighing the acid 
accurately and recording the same. Add about 30 cc. of 
water and 30 cc. 5 normal sulfuric acid and drive off car- 
bon dioxide by heating gently. 

It is seldom necessary to filter after some practice, so 
the solution is titrated hot for the excess of oxalic acid 
with N/10 potassium permanganate solution. Calculate 
amount of oxalic acid oxidized by the pyrolusite. The 
reaction is 

MnOi. + HiCaO* • 2H2O + H2SO4 = MnSO* + 2COs + 4H2O 

Each gram oxalic acid oxidized therefore corre- 
sponds to .6902 g. MnOa. 

89 



As pyrolusite is added to some enamels only to give 
color it is sometimes necessary to know its coloring power, 
and this is dependent upon the total manganese. 

Total Manganese. One-half gram sample is boiled 
with strong hydrochloric acid until chlorine ceases to be 
evolved. The solution is neutralized with calcium carbon- 
ate and an excess of a strong filtered solution of bleaching 
powder is added. The solution is boiled until deep red, 
then alcohol is added until the red color disappears. The 
whole of the manganese now exists as MnOo and may be 
reduced with oxalic acid and titrated for its oxidizing 
power as before with N/10 permanganate of potassium. 
Each gram of oxalic acid oxidized corresponds to .4361 g. 
Mn. 

The Analysis of Soda Ash and Pearl Ash 

Generally it is only necessary to determine the total 
alkali in a sample of either soda ash or pearl ash, and to 
calculate from this the percentage of NaoO or K2O. A 
more complete analysis includes the determination of in- 
soluble matter, iron, chloride, sulfate and moisture, as 
well as the total alkali. 

Insoluble Matter. 50 g, weighed on rough balance 
(sensitive to 0.1 g.) and sufficient water added to dissolve 
the ash, shaking until dissolved. After an hour's digestion 
the solution is filtered through a weighed Gooch crucible 
with a circle of filter paper covering the bottom. This is 
dried at 105° and the increase in weight is insoluble 
matter. 

Iron. The iron in the above insoluble matter is dis- 
solved by pouring hot dilute hydrochloric acid through 
the precipitate in the Gooch crucible. The iron is precipi- 
tated from this by ammonium hydroxide and filtered on a 
white ribbon filter paper. The still moist precipitate is 
dissolved in sulfuric acid, reduced by means of a Jones 
Reductor and titrated with N/10 permanganate. 

90 



Chloride. Three gram samples are dissolved in 
water and nitric acid added until the solution is neutral 
(test with litmus paper). It is then titrated with N/10 
silver nitrate solution. 

Sulfate. Five or ten grams are dissolved in hydro- 
chloric acid and the sulfate precipitated from the almost 
boiling solution by the addition of hot barium chloride 
solution. 

Total Alkali. Twenty-five grams are dissolved in 
water in a 500 cc. volumetric flask and 50 cc. are titrated 
with N. hydrochloric acid, using methyl orange as indi- 
cator. 

Hydroxide. To 50 cc. from above, precipitate all the 
carbonate with barium chloride. Without filtering, add 
phenolphthalein and titrate until colorless with normal 
hydrochloric acid. 

Moisture. Ten gram samples are dried at 120° for 
two hours. 

The Analysis of Saltpeter and Chili Saltpeter 

Moisture. Ten gram samples are heated to constant 
weight in an air-bath at 130°. 

Insoluble Matter. Twenty grams are dissolved in 
boiling water and filtered through a weighed Gooch cru- 
cible with a circle of filter paper on the bottom. After 
drying at 110° in air bath to constant weight, the increase 
in weight is the insoluble matter. 

Chlorine. The solution from above — ^this should be 
about 500 cc. — is placed in a 1000 cc. volumetric flask and 
25 cc. (representing 0.5 g. sample) is titrated with N/10 
silver nitrate, using potassium chromate as indicator. The 
result is calculated to sodium chloride. 

Sulfate. Twenty cc. are heated to boiling and precip- 
itated by adding hot barium chloride solution, a drop at 

91 



a time and with constant stirring. After two hours diges- 
tion ( or until precipitate settles quickly after agitating), 
filter through a Gooch crucible with ignited asbestos filter, 
ignite and weigh as barium sulfate. This is calculated to 
calcium sulfate. 

Calcium and Magnesium. From five hundred cc. of 
the above solution (equal to 10 grams sample) at boiling 
temperature precipitate the calcium as oxalate by the ad- 
dition of ammonium oxalate, being careful not to add 
much excess, as magnesium is to be determined in the 
same sample. Filter on a white ribbon filter paper, after 
an hour's digestion on the steam bath, ignite wet paper in 
platinum crucible, gradually increase to full blast and 
heat to white heat to constant weight. Weight as calcium 
oxide. 

Determine the magnesium in filtrate from the calcium 
by addition of a solution of microcosmic salt and after- 
ward one-third the volume of concentrated ammonium 
hydroxide, added drop by drop. The precipitate, ignited 
separate from the filter paper, is heated at first gently 
and at last with the full heat of a Bunsen burner, and 
weighed as magnesium pyrophosphate (MgaPsO^). 

Perclslorate. Ten grams of the sample of which the 
chloride content has already been determined, is mixed 
with an eiqual quantity of chemically pure sodium carbon- 
ate, and is heated in a large, covered platinum crucible to 
quiet fusion. Ten or fifteen minutes are required. The 
product is then dissolved in nitric acid and the chloride 
estimated as usual. 

Nitrogen. This is determined by the Kjeldahl 
method after reducing the nitrate to ammonia. Twenty 
grams of the sample are ground coarsely and dissolved in 
water in a liter flask, and solution is diluted to the mark. 
Twenty-five cc. (equal to 0.5 g. sample) of this solution is 
mixed in a 800 cc. Kjeldahl flask with 15 cc. concentrated 

92 



sulfuric acid to which 2 grams salicylic acid have been 
added, then add gradually 2 grams zinc dust and shake 
flask to mix contents. Digest over low flame with neck of 
flask slightly inclined until danger of frothing has passed. 
Increase flame until the acid boils briskly and until white 
fumes cease to come off. This usually takes about ten 
minutes. 

Add .7 gram mercuric oxide and continue boiling, 
adding acid if necessary to keep solution from solidifying. 
Solution should be clear in a short time. Complete oxida- 
tion by adding a little powdered potassium permanganate 
and allow the contents to cool. Add about 200 cc. am- 
monia-free water and 25 cc. potassium sulfide solution 
(40 g. commercial salt to the liter) and shake thoroughly. 
Add several pieces of granulated zinc and then pour care- 
fully down the side of the neck 100 cc. sodium hydroxide 
solution (500 g. per liter), avoiding shaking and thereby 
mixing the acid and alkali. After washing the neck with 
ammonia-free water connect the flask immediately with a 
previously set up block tin condenser, which has been 
thoroughly washed and the tips of whose delivery are im- 
mersed in 30 cc. standard acid solution (half normal), 
colored with methyl orange contained in a 150 cc. Phillip's 
flask. Mix contents of digestion flask by shaking thor- 
oughly, then heat carefully, then slowly (taking about an 
hour) distill over 200 cc. of the liquid. Titrate excess of 
acid with standard half normal alkali solution, and from 
this calculate percentage of nitrogen in sample. 

Lung Nitrometer Method. Where frequent analyses 
are made the Lung^ Nitrometer method is better. A nitro- 
meter modified especially for the use of the determination 
of nitrate in saltpeter is here illustrated. The Nitrometer 
"A" and the leveling tube "B" are filled with mercury. 
From a twenty gram sample which has been dried at 110° 
to constant weight as nearly as is possible 0.35 grams is 
put into a weighing tube. This is then accurately weighed 



^Berichte 1886. 18, 1391. 

93 



and the contents shaken into the entry tube "C." The 
weighing tube is again weighed and the difference in 
weight is the grams sample employed. This should be 
close to 0.35 grams so that the gas evolved will be more 
than 100 cc. and less than 130 cc. at ordinary tempera- 
ture and pressure. 

About .5 cc. water is then poured in and the solution 
and crystals (after a minute's standing) are drawn into 
the measuring tube by opening the three-way cock into 
the entry tube "C" and lowering the leveling bulb cau- 
tiously. The cup is washed, using less than 1 cc. of water, 
and about 15 cc. of strong sulfuric acid is admitted 
through the entry tube into the measuring tube. (More 
than 11/2 cc. HgO renders the acid too dilute and the 
mercury is attacked) . After the cock is closed the leveling 
tube is placed in a clamp, the measuring tube is thor- 
oughly shaken and the following reaction takes place: 

MnOa+HsCaO* : 2H20+H2SO*=MnS04+2C02+4H20 

The measuring tube is now placed in clamp on a level 
with the levelling tube and solution is allowed to cool 
for an hour. 

The tube is then accurately leveled, allowing one 
division of mercury for each six and one-half divisions of 
acid, and the gas volume read off. The temperature and 
barometric pressure are read and the gas corrected to 
standard conditions. Each cc. NO gas corresponds to 
.0037986 g. NaNOs or .003845 g. KNO3. 

The Analysis of Cryolite 

Cryolite is a mineral occurring in large quantities in 
Greenland, and is the sodium salt of hydrofluo-aluminic 
acid, NagAlFg. It is used in enamels and is fused, finely 
ground with the frit giving it a milky opaqueness which 
enamellers call "body." It is a very expensive material 
and is most always far from pure, either being deliber- 
ately adulterated or merely naturally impure. 

94 



Methods used by most chemists for its analysis are 
at the best crude. The direct determination of the fluorine 
is the only satisfactory means of properly grading it. The 
method used for cryolite is exactly the same as that em- 
ployed in the analysis of fluorine-bearing enamel as given 
in the beginning of this article, except that one gram of 
the cryolite is finely ground with about three grams (ac- 
curately weighed) of pure silica, and this mixture is fused 
with about eight grams of equal parts of sodium carbon- 
ate and potassium carbonate. In determining the silica 
in the cryolite, this silica which has been added must be 
deducted from that found. 

The alkalies are determined by the method of J. Law- 
rence Smith^ from a gram sample finely powdered. 

Combination of Results. All soda is combined with 
suflftcient fluorine to form sodium fluoride (NaFJ. The 
remainder of the fluorine is combined with aluminum as 
aluminum fluoride (AIF3). The remainder of the alumi- 
num is calculated as alumina (ALOj). 

The Analysis of Fluorspar 

Fluorspar is analyzed especially for the fluorine con- 
tent by the same method as that given under Cryolite. It 
is a material seldom adulterated and a mere fusion with 
six times the weight of sodium carbonate, the taking to 
dryness with hydrochloric acid as in ordinary silicate 
analysis, the removal of iron and alumina as hydroxide 
with ammonia, and the precipitation with ammonium 
oxalate of the calcium and its final weighing as calcium 
oxide, is sufiicient in most cases. All the calcium may be 
calculated as CaFj. The determination of the fluorine, 
however, is of course the only exact method of accurately 
grading this material. 

The approximate method for determining the fluorine 
is as follows : 

Approximate Method for Fluorine. About one gram 
of sample finely ground and accurately weighed is in- 

1 Am. Jour. Science (2) 50. p. 269. Treadwell-Hall Anal. Chem., Vol. II, p. 394. 

95 



timately mixed in agate mortar with about the same quan- 
tity of pure silica. The whole is transferred to a 250 cc. 
Ehrlenmeyer flask — rinsing the mortar with more silica 
The flask is weighed and a weighed quantity of concen- 
trated sulfuric acid is added. The record should now 
show the weight of flask, silica and acid. The flask is 
gently heated and the loss of weight is calculated as sili- 
con fluoride. 

Iron. For use in light colored enamels the iron con- 
tent of the fluorspar is important. Five grams, finely 
ground, are heated in a platinum dish with an excess of 
sulfuric acid as long as hydrofluoric acid is given off. 

After cooling it is diluted with 100 cc. of water, and 
after reducing by drawing through a Jones Reductor the 
solution is titrated with N/10 potassium permanganate 
solution. 

Accurate Method for Fluorine. The fluorine may be 
accurately determined by the following method : 

One gram sample (ground to pass through 200 mesh 
sieve) is mixed with three grams silica and three grams 
each sodium carbonate and potassium carbonate in a 
platinum crucible. Heat gradually until it is in quiet 
fusion. The thin liquid fusion soon changes to a thick 
paste or only sinters somewhat. The reaction is complete 
when there is no further evolution of carbon dioxide. 

After fusion the melt is treated with water and after 
cooling the insoluble residue is filtered off and thoroughly 
washed. The solution contains all fluorine and consider- 
able silica. Remove the silica by adding four grams solid 
ammonium carbonate. Heat liquid at 40 °C. for some 
time and let stand over night. Filter in morning and wash 
with ammonium carbonate water. 

Evaporate on water bath almost to dryness in plati- 
num dish (keep covered, as liquid foams). Dilute with a 
little water. Add a few drops of phenolphthalein. Add 

96 



dilute HCl until colorless. Heat on steam bath and color 
will return. Cool and repeat operation until 1.5 cc. dou- 
ble normal HCl is sufficient to make colorless. Remove 
last traces silica by treating the solution with a solution 
of moist zinc oxide in ammonia water. Boil until am- 
monia is completely expelled. Filter off silica and zinc 
oxide and wash with water. 

Precipitate fluorine as calcium fluoride and calcium 
carbonate by adding an excess of calcium chloride. Filter, 
using blue ribbon paper, and wash thoroughly with hot 
water. Dry precipitate on funnel. Transfer as much as 
possible to a platinum crucible. Burn filter and add ash. 
Ignite contents of crucible. 

After cooling the mass is covered with a slight excess 
of dilute acetic acid (this changes the calcium oxide to 
soluble acetate). Evaporate to dryness on steam bath. 
Take up with water. Filter, wash and dry. Transfer 
most of precipitate to weighed platinum crucible. Burn 
filter paper. Add ash. Ignite and weigh as calcium 
fluoride CaFo. To confirm the results add cautiously little 
concentrated sulfuric acid. Evaporate off excess sulfuric 
acid, ignite and weigh as calcium sulfate. 

The Analysis of Oxides of Antimony 

Arsenic. One gram of oxide of antimony is dis- 
solved in 10 cc. of strong hydrochloric acid — at as low a 
temperature as possible. The solution is then cooled and 
packed in ice and the arsenic, which is almost invariably 
present, is removed by passing through H^S for several 
hours. The As^Sa is filtered off in a weighed Gooch cru- 
cible, washed first with CS2 and alcohol then with concen- 
trated hydrochloric acid and dried at 100°, and weighed 
as .r\.S203. 

Antimony. The filtrate from above is put into 250 cc. 
volumetric flask, rinsing the beaker well with concen- 
trated hydrochloric acid and an equal part of water. All 

97 



the HoS is removed by passing through a current of air. 
Five grams of tartaric acid are added and the liquid 
diluted to the mark. 

Twenty-five cc. of the solution are measured out with 
a pipette and are neutralized with dry sodium bi-car- 
bonate — keeping covered to avoid loss — finally a pinch of 
sodium bi-carbonate and a cubic centimeter of clear 
starch solution is added and the mixture is titrated with 
N/10 iodine solution. 

1 cc. N/IO Iodine = 0.0060 grains Sb 

The Analysis of Oxide of Cobalt 

Arsemc, One gram finely pulverized sample is fused 
at low heat with ten grams bisulfate of potassium for 
three hours. The melt is extracted with water acidified 
v/ith sulfuric acid and the arsenic is precipitated from the 
warm acid solution with HgS, collected in a weighed 
Gooch crucible, washed v/ith water containing HgS and 
dried at 100° for one hour and weighed as ASgSg. 

Cobalt. The filtrate from above is boiled, and at the 
same time air is drawn through to remove the HoS, and it 
is then treated by Fisher's Potassium Nitrite method^ to 
separate the cobalt and the nickel. 

The concentrated solution containing salts of both 
metals is treated with pure potassium hydroxide to alka- 
line reaction, made slightly acid v/ith acetic acid, and to 
this a concentrated solution of pure potassium nitrite 
that has been made slightly acid with acetic acid is added. 
After vigorous stirring, the mixture is allowed to stand 
twenty-four hours in a warm place. Before filtering, a 
little of the clear solution is pipetted off and treated with 
more potassium nitrite to see if the precipitation of the 
cobalt has been complete. If a precipitate is formed, the 
whole solution is treated v/ith more potassium nitrite and 
again allowed to stand until complete precipitation is ef- 



'TreadweU, Vol. II, p. 130. 

98 



fected. The precipitate is then filtered and washed with 
a barely acid 5 per cent solution of potassium nitrite until 
1 cc. of the filtrate, after being boiled with hydrochloric 
acid and treated with caustic potash and bromine water, 
no longer gives a black precipitate of nickelic hydroxide. 
The cobalt precipitate is then transferred to a porcelain 
dish, covered, and hydrochloric acid is gradually added 
until there is no further evolution of nitric oxide, and 
after filtering, the cobalt is precipitated by means of caus- 
tic potash and bromine water. 

The precipitate is filtered off, using blue ribbon filter 
paper, dried, and ignited. After cooling it is treated with 
water in order to remove the small amount of alkali which 
is always present, after which the residue is ignited in a 
stream of hydrogen and weighed as metal. After weigh- 
ing, the metal is dissolved in hydrochloric acid, evapor- 
ated to dryness, the dry mass moistened with hydrochlor- 
ic acid, then treated with water, and the small residue of 
silicic acid is filtered off. This residue is ignited and its 
weight subtracted from that obtained after the ignition 
in hydrogen. 

Nickel. The filtrate containing the nickel is treated 
with hydrochloric acid until the nitrite is completely de- 
composed, and the nickel is precipitated with potassium 
hydroxide and bromine water as brownish-black nickelic 
hydroxide [Ni (OH) 3.] 

The precipitate — which seldom contains more than 
ten milligrams of nickel — is washed with hot water, col- 
lected on a filter and is dried, ignited separately from 
the filter, and weighed as NiO, in which form it was prob- 
ably present in the oxide. 

Steel Plate 

The steel best adapted for enameled ware is of very 
low carbon value and extremely low in the other impuri- 
ties, in fact, the nearer pure iron the better. Of the steel 

99 



plate used by the Columbian Enameling and Stamping 
Company, the best satisfaction was obtained from those 
giving the following analysis: 

Sulfur from .040% to .050% ; phosphorous from 
.030% to ,090%; silica less than .01%; manganese from 
.060% to .040%, and carbon less than 0.10%. The sheets 
must be of an even gauge for seamless drawn work and of 
a dark soft quality, which allows them to be drawn with- 
out tearing. When the vessel is made without drawing and 
sheets are used flat, this evenness of gauge is not so much 
an object. The grain in all cases must be as open as pos- 
sible. The sheet must be low in carbon and sulfur, as 
these develop gases at temperatures of the muffle, which 
would cause the enamel to peel off. 

Samples of the steel plate are obtained from drillings 
taken from eight or ten sheets stacked in a pile, and 
drilled holes are run every two inches on the diagonal of 
the plate. Drillings are sampled down to twenty-five 
grams, which are kept in stoppered bottles. The method 
of analysis is that commonly employed by steel-works 
chemists, and can easily be found in print elsewhere, and 
for that reason will not be given here. 



100 



ATOMIC AND MOLECULAR WEIGHTS AND 

FACTORS USED IN CERAMIC 

CALCULATIONS! 



Aiuminum, 












oxide, 
hydrate. 




AI3O3 

Al,03 


*102.2 
.3H2O 156.3 


tR,03- 
R.O3 


— 102 

— 156 




1 Al — oxide 


= 1.529 Al— hydrate 

= 6.536 Al— sulfate 

=: 8.893 Ammonia Alum 

:= 2.534 China Clay 

= 2.548 Cryolite 

= 9.305 Potash Alum 

= 5.154 Soda Feldspar 

= 3.069 Am. Enamel Clay 




Antimony, 












oxide, 
tetroxide, 
pentoxide, 
sulfide. 




Sb,03 

Sb^O, 
Sb.,S, 


288.4 
304.4 
320.4 
336.6 


R2O3 
R2O3 
R2O3 
R2O3 


— 288 

— 304 

— 320 

— 337 




1 Sb — trioxide 


= 1.167 Sb— trisulfide 
= 1.111 Sb— pentoxide 






Arsenic, trioxide. 


AS2O3 


197.9 


R2O3 


198 


Barium, 












carbonate, 
sulfate, 




BaCO 
BaSO 


197.4 
233.4 


RO 
RO 


— 197 
233 




1 Ba — carb. 
1 Ba — oxide 
1 Ba— sulfate 


= 0.777 Ba— oxide 
= 1.287 Ba— carb. 
= 0.657 Ba — oxide 






Boric Acid, 


B,03. 


3H,0 


124.0 B^O 


3 


124 


(Fused), 


B.O3 




70.0 B2O 


3 


70 


Borax, 


Na^B^O.-lOH^O 382.2 RO. 


2B,03 


382 


(Fused), 


Na.B^O, 

1 Boric Acid 

1 BaOs 

1 Borax 

1 Borax 

1 Borax 

1 Borax (Fused) 

1 Borax " 

1 Borax " 


202.0 RO. 

= 0.548 B2O3 

= 1.771 Boric Acid 

= 0.529 Borax Fused 

= 0.162 Na— oxide 

= 0.366 BoOs 

= 0.307 Na — oxide 

= 0.693 B0O3 

= 1.892 Borax 


2B3O3 


202 



1 Compiled by Robert D. Landrum, mainly from Report of Committee of Equiva- 
lent Weights, Transactions of American Ceramic Society, Vol. II, pages 196 to 278. 
The reader is referred to this report for full explanation and method of using these 
equivalent weights. 

♦Molecular Weight. tEquivalent Weight. 



101 



Cadmium sulfide, 

Calcium, 

carbonate, 

fluoride, 

oxide, 

phosphate, 

sulphate, 



CdS 



*144.5 tCdS —145 



CaCOg 

CaFa 

CaO 

Ca3(P0J, 

CaS0,.2H,0 

1 Ca — fluoride 



100.1 

78.1 

56.1 

310.3 

172.2 



RO 
RO 
RO 
RO 
RO 



100 

78 

56 

103 

172 



= 0.718 Ca — oxide 
= 0.487 F. 

1 Ca — oxide = 1.786 Ca — carbonate 

" =1.321 Ca— hydrate 

" = 3.073 Ca— sulfate (Gypsum) 

1 Ca — ^phosphate = 0.542 Ca — oxide 



China Clay, 



Al2032SiO, 
2HoO 



Cerium 

dioxide, 
sesquioxide, 

Chromate of Barium, BaCr04 



CeO^ 
Ce,0, 



Chromate of Lead, 
Chromium Oxide, 



PbCrO^ 
Cr,03 



258.0 



172.3 
328.3 

253.5 



323.1 



152.0 



R2O3] 
2SiOj 



CeO^ 
R2O3 

2R0 
R2O3 

2R0 
R2O3 

2R0 
R,0, 



I- 
i- 
i- 



258 

172 
328 

506 

646 

152 



Cobalt 

carbonate, 

chloride, 

nitrate, 

oxide, 

oxide, 

oxide (blk.); 

sulphate. 



1 Cr — oxide = 1.6B8 Am — ^bichromate 

" = 2.001 Am — chromate 

■" = 1.828 Cr— hydrate 

" = 5.261 Cr — nitrate 

" = 4.710 Cr— sulfate 

" = 6.288 Cr — ammonia alum 



C0CO3 119.0 RO 

C0CI2.6H2O 238.0 RO 

Co(N03)2.6H20 291.1 RO 

CO2O3 166.0 RO 

CoO 75.0 RO 

CO3O4 241.0 RO 

CoS0..7H,0 281.2 RO 



119 

238 

291 

83 

75 

80 

281 



1 Co — carbonate 
1 Co — chloride 
1 Co — nitrate 
1 Co — ic oxide 
1 Co — ous oxide 



0.630 
0.315 
0.258 
0.904 
1.587 
3.173 
1.173 
3.749 



Co — ous oxide 
Co — ous oxide 
Co — ous oxide 
Co — ous oxide 
Co — carbonate 
Co — chloride 
Co — ic oxide 
Co — sulfate 



♦Molecular Weight. fEquivalent Weight. 

102 



Copper 

oxide (red) Cu^O *143.1 fRO — 72 

oxide (black) CuO 79.6 RO — 80 

sulphate, CuSO^.SH^O 249.7 RO — 250 

1 Cu— oxide (Blk.) = 0.899 Cu— oxide (Red) 

1 Cu— oxide (Blk.) = 3.137 Cu— sulfate 

1 Cu— oxide (Red) = 1.112 Cu— oxide (Blk.) 

1 Cu— sulfate = 0.319 Cu — oxide (Blk.) 

Cornwall Stone, IRO . 2.5 AI2O3 

20.SiO2 1550.0 IRO] 

2.5R2O3fl550 
20.0 SiOJ 

Cryolite Na^AlF^ 210.0 3R0 1 

Al.Osj— 420 

Feldspar (Soda) Na^O.Al^Og 524.0 IRO] 

6SiO, IR2O3I — 524 



6SiO 



t 



Feldspar (Lime-Soda)CaO) Al^Og 520.0 IRO 1 

Na^O) 5Si02 IR^Ogf— 520 



5SiO 



Feldspar (Potash) K^O.Al^Og 557.0 IRO] 

eSiO^ IR2O3I — 557 

6SiOj 

Ferric Oxide Fe^Og 159.7 R2O3 — 160 

Ferrous Sulphide FeS 87.9 R2O3 —176 

Ferric Oxide 

(Magnetic) Fe304 231.5 R2O3 —155 

Ferrous Sulphate FeSO,.7HoO 278.0 R^O, —556 

Lead Acetate Pb (0311302)2 

3H2O 379.2 RO —379 
carbonate (basic) 2(PbC03) 

Pb(OH). 775.3 RO —258 

oxide (red) PbgO, 685.3 RO — 228 

Litharge PbO 223.1 RO —222 

Magnesium 

carbonate MgCOg 84.3 RO — 84 

oxide MgO 40.3 RO — 40 

1 Mg — carbonate = 0.479 Mg — oxide 

1 Mg — oxide ^ 2.089 Mg — carbonate 



*Molecular Weight. tEquivalent Weight. 

103 



carbonate 




MnCOg 


*114.9 


tRO — 


115 


di-oxide 




MnO, 


86.9 


RO — 


• 87 


Nickelic Oxide 




NiO 


74.7 


RO — 


• 75 


Nickelous Oxide 




Ni,03 


165.4 


RO — 


• 83 


Nickel Sulfate 




NiSO^.TH^O 280.9 


RO — 


■281 




1 NisC 


)3 = 


0.903 NiO 








1 NiO 


= 


1.107 NiaOs 








1 NiO 


= 


3.760 Ni — sulfate 






Potasli Alum 




K,S0,A1,(S0,)3 














RO 








24H,0 


949.1 


Al,03 - 


-949 


Potassium 












antimonate 




KSbOs 


207.3 


RO 

Sb^O, - 


-414 


bichromate 




K^Cr^O, 


294.2 


RO 1— 

2R.O3J- 


-294 


carbonate 




K.COs. 


2H2O 174.2 


RO — 


-174 


carbonate 
(calcined) 




K2CO3 


138.2 


RO — 


-138 


nitrate 




KNO3 


101.1 


RO — 


-202 


1 


K — nitrate = 


0.466 K — oxide 








" 


= 


0.683 K — carbonate 








" 


:= 


0.737 K— chloride 








" 


= 


0.863 K— sulfate 






1 


K— oxide = 


1.467 K — carbonate 


(anhydrous) 






" 


= 


1.848 K — carbonate 


(crystal) 






" 


=z 


1.582 K— chloride 








" 


= 


1.192 K— hydrate 








" 


= 


2.145 K— nitrate 








" 


= 


1.849 K— sulfate 








« 


r= 


5.927 K — feldspar 








" 


= 


10.066 K— alum 






Selenium 




Se 


79.2 


SeO^ — 


- 79 


Oxide 




SeO^ 


111.2 


SeO^ — 


-111 


Silica 




SiO, 


60.3 


SiO, — 


- 60 



*Molecular Weight. fEquivalent Weight. 

104 



Sodium 



antimonate NaSbOg * 191.2 fROSboO-— 


•382 


carb. (cryst.) Na2CO3.10H2O 286.2 RO "— 


■286 


carb. (soda ash) NagCOg 106.0 RO — 


106 


chloride NaCl 58.5 RO — 


117 


hydrate NaOH 40.0 RO 


80 


nitrate NaNOg 85.0 RO 


170 


silico fluoride Na^SiFe 188.3 ROSiF^ — 


189 


1 Na — carbonate 




(crystals) = 0.371 Na— carbonate (anhydrous) 




1 Na — carbonate 




(crystals) = 0.216 NaaO 




1 Na carbonate 2.698 Na — carbonate (crystal) 




(anhydrous) = 0.585 NaaO 




1 Na carbonate 0.531 NaaO 




(anhydrous) = 0.774 NaaO 




1 Na — chloride = 0.365 NaaO 




1 Na — hydrate = 6.161 Borax (crystal) 




1 Na— nitrate = 3.258 Borax (anhydrous) 




1 NazO = 4.613 Na— carbonate (crystal) 




" = 1.710 Na — carbonate (anhydrous) 




= 1.887 Na— chloride 




" =1.290 Na— hydrate 




" = 2.742 Na— nitrate 




= 5.193 Na— sulfate (crystal) 




= 2.290 Na— sulfate (anhydrous) 




= 8.500 Na— feldspar 





Strontium 










carbonate 
sulfate 

Tin 


SrCOg 
SrSO, 


147.6 
183.7 


RO 
RO 


148 
— 184 


chloride 
oxide 


SnC1..2H,0 
SnO, 


226.0 
151.0 


RO 
RO 


— 226 
151 



Titanium Oxide 



TiO., 



80.0 TiO,— 80 



Uranium 










oxide 

oxide (com'l) 


UO2 

Na,O.U. 
6H,0 


.o« 


270.5 R2O3— 

746.0 RO 1 

R2O3J- 


-543 
-746 


Zirconium Oxide 


ZrO^ 

tEquivalent Weight. 

105 




122.6 ZrO^ — 


-123 


* Molecular Weight. 





CUBICAL COEFFICIENT OF EXPANSION 

in Millimeters per degree Centigrade, as determined 
by Winkelmann and Schott and Mayer and Havas 

(See Sprechsaal 1911, No. 13) 

AIF3 = 4,4 X 10-^ MgO = 0.1 X 10-^ 

AI2O3 = 5.0 X 10-^ MnO = 0.1 X 10"^ 

AS2O5 = 2.0 X 10-^ NagAlFg = 7.4 X 10"^ 

BaO = 3.0 X 10-^ NaF = 7.4 X 10"^ 

BeO = 4.7 X 10-^ Na^O =10.0 X 10"^ 

B2O3 = 0.1 X 10-^ NiO = 4.0 X 10-^ 

CaF^ = 2.5 X 10-^ PbO = 4.2 X 10"^ 

CaO = 5.0 X 10-^ P2O5 = 2.0 X 10-^ 

CeO^ = 4.2 X 10-^ Sb.Og = 3.6 X 10"^ 

CoO = 4.4 X 10-^ SiO^ = 0.8 X 10"^ 

Cr^Os = 5.1 X 10-^ SnO^ = 2.0 X 10"^ 

CuO = 2.2 X 10-^ ThO^ = 6.3 X 10"^ 

Fe^Og = 4.0 X 10-^ TiO^ = 4.1 X 10"^ 

K^O = 8.5 X 10-^ ZrO, = 2.1 X 10"^ 

LiO. = 2.0 X 10-^ ZnO = 1.8 X 10"^ 



106 



237 90 




\ 









.0- 




0^ olV- ^ V 











HECKMAN t 

BINDERY INC. p 

.^ MAY 90 









